its pretty simple, download the 1.3 patch for the game (required for mods you dum dum heads)

here's one of the links to it, you can probably find it in other places tbh: https://www.moddb.com/games/star-wars-battlefront-ii/downloads/the-unofficial-v13-patch-revision-129-final

please for the love of god, DO NOT MAKE YOUR OWN ADDON FOLDER. The patch will create it's own folder for addons, putting your own in will ♥♥♥♥ everything up.

once the patch is downloaded, go through the installation process (make sure the place the patch is going is where the game is located and all that jazz) also a side note, make sure the 1.2 hud option you'll see in the installer is disabled because it is absolute garbage.

and there you go, place any and all addons into the addon folder (if they are zipped or in a .rar format, get winrar or just unzip/extract the contents into the addon folder the 1.3 patch has made.)

Some addons you'll just have to research how to add them in because they dont want to be put into the addon folder and actually work because idk

and please, do n o t make your own addon folder at any point during this otherwise you have the big dumb