We will go over:

• Files
  
• Finding in files
  
• What to add
  
• Final product

To add a vehicle you must first find the file to add it. Just go to resource\set\multiplayer\units and pick whatever "vehicles_XXX" faction you want to edit. I will do "vehicles_ger2". I recommend notepad++ but you can use notes.



Now I recommend you make a copy of the file you want to edit as a backup, but you do you.

Now these files aren't that large so you shouldn't easily get lost in them.
This is what you can find (This is already edited).

As an example, I will add the Panzer IV with a narrow turret to the list. Now before adding it we should know how many crewmember it takes in. I know that that is 4.

This is what the list looks like before edit (In the tutorial):


All you need to do add the vehicle is to copy one of the vehicle lines in the file:


And make a new line with it like this. I recommend having it last in the list:

There are some details we will to change about it. The first is the entity file it is looking for, which is the .def file's name. For the panzer IV with NT it would be "panzeriv_k".


Just change the "pz4h_ger2" to "panzeriv_k".
Now since the tank holds 4 crewmembers instead of 5, we will need to change the crew that will be inside it, which is the "n1(4)" and "n2(1)" value. The n1 is the tankman and n2 is the tankman2 (tankcommander). We will change n1 from 4 to 3.

A very important value to change is the "g(e4)" value. It must be unique. Change it to a unique value in the ;°°°Button 4°°° section. Now I will change 4 to 11 but since you don't have any other new vehicles you can change it to something other.
I will not go so much more in depth of the other values as you can just experiment and gain experience from it yourself ;)
The final line should be like this.


That should be it!

After doing this and trying skirmish again and tada!


Now if you see this but are able to spawn it correctly:


Then it is not from my end. There is simply no "unit_icon" file for it in "resource/interface/scene/unit_icon".

That should be it!

Edit: Note that AI player will sadly not be able to use these vehicles in skirmish. The closes to it would be by "donating" it to your AI teammates.
There might be a way to make bots use the modded vehicles in the bot.data.lua file in resource/script/multiplayer.