By the way, I forgot to add that this a a singleplayer and coop map, and I know how to make it compatible with these gametypes, but I just need to know how to make the .gro file and what goes into my created "Levels" folder in Content/SeriousSamHD_TSE/Levels, and once again the "Levels" folder is one I created and I added a .nfo file using wordpad inside that folder already with the same name as the episode folder within the Levels folder. That's all probably a bunch but I hope it's understandable.

Both can be done with the editor. Just go File, and you should have options like gro packing and steam workshop uploading there.

I noticed that earlier, and when I click the option to create a .gro file I get an error at the bottom saying
" Invocation of 'zip' command failed with error code 1. For proper operation, make sure you have Info-ZIP's (http://www.info-zip.org"

After looking at that, I click on the link to get the software, but I have no idea what to download (since there are several links) and I don't know where to put this download.

Oh wow, it's not yet implemented in SSHD? I thought it was... well nevermind then. The other ways of making a gro is:

1. Copy an official one, rename it, and delete everything from it (but there should be always a file in it or it won't work; you can delete that file after you copied over your files), then copy your files into it.

2. Make a zip archive and just rename it into a gro. A gro file is just a renamed zip file, however it might not work always, because a gro is a -specific- kind of zip, that your zip archiver might not do by default (but most of the time it does).

How do you make a .nfo file then, like, what are it's parameters? Also, what do you put for each REQUIRED parameter? Required meaning everything needed to function and putting a preview image in the menu.

You copy an offical nfo file and then modify it. The only requirements for your map to function is to have the nfo file near the wld file, and it must have the same name. Anything written in it is optimal (with the exception of the line with the game modes).

Preview images (aka thumbnails) you have to make yourself. It must be a tga file with the size 512X256, which then you make into a tex file with the editor (Texture->Create texture).

Ok, so now when I open the .nfo file from a level or episode in the official area, and then I create everything I need for my level to try and get it to work on the actual game, I get an error as so:
-----------------------------------------------------------------------------------------------------------------------------------

Episode Error -

Content/SeriousSamHD_TSE/Levels/Sands of Desperaton.nfo: Cannot open file (error code: 32)

-----------------------------------------------------------------------------------------------------------------------------------

Level Error -

Content/SeriousSamHD_TSE/Levels/Sands of Desperation/Operation Kill Everything Ahead.nfo: Cannot open file (error code: 32)

-----------------------------------------------------------------------------------------------------------------------------------

.nfo level parameters

LEVEL
GAME_MODES="SinglePlayer; Cooperative; CooperativeCoinOp; BeastHunt; TeamBeastHunt;"
LOCKED="No"
LOADING_SCREEN=
NAME="TTRS:7_01_Operation Kill Everything Ahead.Name=Operation Kill Everything Ahead"
THUMBNAIL=
ETA="00:40:00"
TIMEBONUSMUL="3.5"
DLCID="SeriousSamHD_TSE";

NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/sniper.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/flamer.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/rocketlauncher.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/tommygun.rsc"

NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/SingleShotgun.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/doubleshotgun.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/Colt.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/chainsaw.rsc"
NETRICSA="Content/SeriousSamHD/Databases/Messages/Weapons/KNIFE.rsc"

-----------------------------------------------------------------------------------------------------------------------------------

.nfo Episode parameters

EPISODE
NAME="TTRS:Episode.Sands of Desperation=Sands of Desperation"
THUMBNAIL=

-----------------------------------------------------------------------------------------------------------------------------------

The name of the episode is "Sands of Desperation"

The name of the level is "Operation Kill Everything Ahead", which is the name of the .gro file and the .wld file withing the episode folder.

You musn't have space in the filename, the game won't read them properly. So the gro file should be named "OperationKillEverythingAhead" or "Operation_Kill_Everything_Ahead". Same about the wld and folder names too.

Ok, how come I can't reopen them in the editor like I can with an official .nfo?

I definitely screwed something up. I can't start the editor or the game itself now. Heres the error I have to type out completely:

Cannot load
'Content/SeriousSamHD/Databases?GlobalGameParameters.rsc':
Stream is signed with insufficient credentials.
(Content/SeriousSamHD/Textures/Decals/Blood/Green_Debris_BloodStain_01.rsc)

That's the whole error, and I already tried reinstalling both the game and the editor. I STILL have this problem, and I have no idea what on Earth I screwed up now.

...Did you change any of those files? Did you maybe extract them from their own gro? (You can't extract things from official gro files.)

Are you sure you're not opted into publicbeta with the game, but not the editor?

And really, just what did you do?

I edited an official .gro file, made my own parameters for it, then saved it with a different name in a different folder, so I made sure it wouldn't overwrite anything.

Umm, you copied that official gro right? Not just renamed it. Also, you have to delete everything from it, or it will give you credential errors. Only put the things in it that you have changed using the editor.

So make it myself? Well I can't do anything of the matter because nothing SS TSE HD related will open. So I'm pretty confused.

You just have to delete that gro you made. When I said that you need to take an original gro, I said to copy that gro (maybe one of those DLC character ones, they are small) delete everything from it, then put your own files into it. You should also give it a unique name.