How do you use nonsteam games in garrys mod?

Just wondering how I would for instance use a non steam counter strike in garrys mod? Like how do I get garrys mod to detect it or whatever. I got garrys mod off of steam and I also own half life 2 deathmatch I just want counter strike for the models and such. Help would be most appreciated :smiley:

Counter-Strike isn’t compatible for Garry’s Mod mounting. Counter-Strike: Source is. CS:S requires itself to be added to Steam for legitimate usage.