Alright, so TTT weapons are like this, there is a folder with a name like: "ttt_weapon_name". Inside this folder there's a file, which is always called "shared.lua".
TTT weapons are located here: -Garry's Mod server directory-/garrysmod/gamemodes/terrortown/entities/weapons/
Drag the "ttt_weapon_name" folder into the directory I showed you. Now the weapon you added should spawn automatically, if the map supports "random weapon spawn". If it doesn't, you may have to add that yourself using the TTT Weapon Placer. A tutorial on how to do this can be found by
clicking here.