How do I get retail to work with beta models?

[ShabRBM47]

I'm working on a mod with a very small team right now, and I do not know the technical side of hammer at all. I want to use the beta models but I don't know how to get the game to use the models I want. I want to replace the NPCs though. I'm sorry if my question was all over the place. Any help would be appreciated.

[Stepa2]

You can get world models here.
Some NPC model replacements are here.
If you need leak world materials, you can get them from this pack.