I guess you don't have much experience with incel mapstaring games
I'm not saying you should play more of that shit but I know how the gay ass launcher works but it is rather complicated to deal with without steam handholding you
So you have to get all the mods and put it in the mod folder in your stellaris folder in your documents folder, the folder and the .mod file next to each other with the same name
the .mod file should look something like this if it says something different for you
here's the wiki page as a reference in case you run into anything outside the scope of this reply:
https://stellaris.paradoxwikis.com/Modding 