The Estab Editor is a bit of a complex modding tool of sorts in which you can create your own weapons, ammo, vechicles and forces.
Set up note:
When setting up an Estab the game will first load it in an older file format, first set up two Estab Sides and name them whatever you want, to do this go to the sides tab and right click to add New side. It is important to give these two sides or any at all a BMP icon which you can easily get from the BEF Estab (The game's orignal estab folder and copy the contents to the Estab you using, this is commonly named (Your Estab_Images) keep note that your name may differ although the estab will default to _Images which helps.)

What happens if you don't set the sides BMP images: Simple, the game crashes when you launch Scenario maker and try to use your .coe file.

Another big tip for a simple this guide is to look at the Estab Edtior manual in the documents folder in Command Ops 2.

DO NOT change the base .COE file whatsoever. Copy and paste it before you do anything with it and its XML file (IF you have one)

What do if you can't find base game XML file:
Welcome to how i learned to do this. Create a new Estab file from scratch.

How to get better with Estabs:
Download steam workshop Estabs and launch them in scenario maker and add notes of how the steam workshop creators did their estab. You can custom a variety of things in Estab.

Setting up weapons:
You can select their type but to get an historically accurate weapon when reinventing the Estab wheel is to search a weapon you want and copy and convert the measurements into metres (ignore barrel length as it is irrelevant for the Estab in terms of data). You can only get a limited amount of distances of around maybe 5-6. I keep my first range to 200 metres in general although you can use 100 metres if you want and try to keep things close to the maximum number in mind (also try to avoid making some guns have ridiculous ranges to avoid unfairness in game).
It is also advised to load the base game and look at some weapons and vehicles to add some correct details such as payload and towing capacity or get a good gauge

Steam players warning:
The manual says when creating a new Estab you are to create a copy of the XML file of the base game, however many of you will probably check and only see the .Coe file only and no XML file. Some users in a forum were talking about this issue and one of them said it was "fixed". It seems that with the steam version you are bascially having to make an estab editor file from scratch.

Setting up forces:
Add names and images to the Sides. the service forces can actually go without any image for testing but the Sides need an image to work. Copy and paste the base game images into your named ESTAB file image folder. You dont even need to close the game to do this as it wont mess anything up.
Look at the manual of the guide to get a good idea what your forces should be like. Add ranks around 6-8 will do and name them accordingly (best to do research for rank names.

Fictional weapons:
Fictional weapons and vehicles are very odd to try and get into the game. Doable but some but the measurements are an issue. Make reasonable estimates of the height and length or use a real life tank measurements as a baseline. Same for weapons. For Example the Mark 2 lancer assault weapon is a fictional gun based modern day weapons so use something like an modern day rifle for measurements. I ignore the barrel length for the overall length. Width i honestly put around 0.5 - 10% of the length.

Some weapons will actually state their rate of fire so roughly divide the max value for the normal fire rate and a further 2 for the slow rate. Bolt action rifles like the Lee enfield say they have a fire rate of 20-30 rounds per min so what i do there is take 10 off the max rate for the normal and another 10 off for the slow rate. Real life weapons are easier to get their fire rate and measurements.
Shell weight: Most annoying bloody thing. Put the blast radius for 0 for small arms fire. Rockets and rpgs have their own sections. Most small arm weapons are anti personnel unless you are trying to do something like the Bolter from warhammer 40k.

Force supplies:
Honestly use a guide. I don't know anything properly on this section. W.I.P.

Is this guide good: Honestly probably not but it is better than nothing.