Ever wondering how to add HL2 ep 1/2 contents on Gmod? Or L4D 1/2 contents? Here i come!
Step 1: Launch Gmod, as usual.
Step 2: Wait till it loads, then go to the right-down corner of your screen (If fullscreen) or the Gmod page.
Step 3: You may see a really tiny joystick, click on it.
Alright, when you clicked on it, you see a list of the games you have in bright white, and games you don't have in dark white
You just need to tick the games you want the contents to be added, and there you go!
Step 4: Have fun!