I am going to give a few basics on what commands do what.

left click on a character to select that character.
left click and drag to select a bunch of characters.
right click to move, or interact or or cancel an interaction this last part is very important to cancel a searching unit in order for it to defend itself. (I normally right click on said unit to make them go on standby.)
R is for manual reload. THIS DOES NOT CONSUME AMMO.

that is all I figured out for now.

starting out you have little options for things. In fact depending on what you chose you will have 3 (or 4 if you chose medic class) options after you get past the tutorial.

in the center of the map will be landmarks. These are mission areas. Here is a rule of thumb. higher rank areas are normally more difficult but in return have more resources.

a house for example is a level 1 rank mission. they will have typically a few wood piles, some food and perhaps another resource such as ammo, medical supplies or fuel. these maps I typically call 90 seconds maps. because unless you managed to make your team a solo (in which I recommend a restart) then these maps can easily be cleared by a 2-3 man team in 90 or so seconds.

a police station on the other hand is a rank 3 structure. it contains lots of ammo, at least 1 special objective, and usually armor or weapons parts as well as some other things. However, they are much larger than a house and usually have several points of entry for eaters. This place is impossible for solos, and even only duo teams can easily be wiped out.

you can tell how high of a rank a landmark is by the number of squares under it. Speaking of squares. (or ap) you can find how many you have at the top of the world map. there is 4 visual effects related to these ap. The first is an empty square. Which means you do not have enough ap generation to 'normally' fill this square in. (but you can still fill it doing certain events or interacting with maps in missions) the next indicator is a grey square. This means you had ap generation to have it to here but have used it already. The third is the white ap squares. This is the amount of ap you currently have. Any glowing ap means that will be the cost of your total ap for the action your mouse is hovering over.

Next I will explain the icons in the top left corner. first and all importantly, is the save action. DO NOTE: it does cost both food and ap to use this action.

The next icon of a person is to look for someone. This can help you find a new person for your team, or help you find other random people. Some I have found are the homeless, the pilot, the trader, the teacher, the commander (this one might have been an event), the scientist. more on these people later.

Next (if you have a medic on the team) is the treat icon, which cost 2 and some medicine. but will full heal your team (10 hp to 1 medicine or something like that. do not know exact ratio, but normally costs me about 40 by act 3)

the last one I found so far is scavenge. which will add 50 random resource (might be different for ammo and upgrade parts) which is good if your team is low hp or ammo. or you ran out of places to look due to lacking ap (or searching them all already.

In the bottom left corner of the map after you unlock it is the morale, agro, and evolution meters. higher agro means eaters will find you in missions faster and spawn both more anad more often.
Morale, affects your teams speed of doing actions. from interacting/looting to movement. basically the lower your morale is the worse your units perform. (This statement might not be true.)
evolution means what variety of units come at you.

on the bottom of the screen is your upgrade tabs. once you unlock them they will be unit trainer, armory, workshop, and research.

trainer and armory unlock after area 1. the trainer allows you to level up your heros into one of six special stats. (note, I find it best to have at least 1 point in every catagory for each unit)
armory upgrades your individual units gear. weapons and armor parts will be used here, but for medic and engineers, they will also use tools and meds repectively upgrading their unique gear for them.
the workshop, unlocked after area 3 (I think) will allow your vehicle to be upgraded. more fuel effency, more ap per day, higher cap to unit limit. Do note that these upgrades are expensive on tools.
finally we have research (which is after area 4 I believe) this allows for general unlocks for just about everything else. from more ap, to researching missing gear upgrades, to resting and training. cheaper healing. and so much more.

on the bottom right corner we have days left, progress of satilite and progress of vaccine

as I said before, right click your selected unit to make them stop their current action. THIS IS IMPORTANT!!!

early on, it might seem like a good idea to just kill, Kill, KILL, but you will soon find out you have a finite amount of bullets... opps (especially if you pick up a unit that eats ammo like popcorn.)

Some basic tips early on.

If there is no window or halls with bloody batches down them, that likely means you have no zombie spawns OPPS, I mean eater spawns in your starter location.that means the map is essentially paused. take this time to look around for resources and plan your pathing. do you want to go through 4 doors for 20 medical supplies and 30 wood along the way to it, or would you rather go through 3 doors and get 50 food and 10 wood along the way. Each choice has pros and cons. Here is my list of items ranging from most important to least.

ammoP
ammoS
interact: map
interact: generator
interact: blueprints
interact: radar/vaccine
tools
fuel
armor/weapon parts
meds
food
wood

(there are a few things that I forgot on there and some are situational as well)

In all it is a risk + cost in ammo = reward in resource game. and later on you ARE going to run low/out of ammo.

to go very simple I try to make my units have a build in addition to their class.

for example, engineers I normally pump up looting and interactions.

F- 1
B- 1
R- 3
I- 3
M- 1
P (intuition) -3

then I have brawling tanks that can hold a doorway.

F- 3
B-3
R-1
I- 1
M- 3
P- 1

gun runners that either loot or shoot

F- 2
B- 2
R--2
I- 2
M- 2
P- 2

front line medic

F- 3
B- 3
R- 3
I- 1
M- 1
P- 1

and so on...

in general, this game is hard. but fun. It is important to note that there are unlocks. these unlocks (seen in the main menu) grant bonuses to starting materials, not a lot, but enough. it is fine to fail. as long as you try again. experiment, maybe not loot everything not nailed down and be picky. or play more aggressive for that much needed loot.