That's cleared up, let's address the 'how'. You'll need Garry's Mod 13, the current beta that Garry's been developing for the last year. If you have GMod on Steam you'll now have access to the beta.

Official Garry's Mod spiritual sequel Sandbox is finally available for everyone to try, letting you make any game mode you can think of.

With all the hours you've probably put into Garry's Mod, saving your game world is a must. Luckily, there's an easy way to save your progress and make sure any of your projects aren't wiped.

Source Engine-powered Garry's Mod is a robust physics sandbox, commonly used for putting silly faces on familiar Half-Life characters.