From BunglistBuild Gmod Wiki
[edit] Installation
* Get TortoiseSVN (You must select 32 or 64 bit version, Don't know? Look it up!) [1]
* Find your Addons folder.
* Usually its here: C:\Program Files\Steam\Steamapps\<username>\garrysmod\garrysmod\addons\
* Make a folder in the Addons folder. Call it SB3
* Right Click the SB3 folder you made and choose "SVN Checkout"
* In the "URL of Repository" box, copy and paste this link: http://customaddons.googlecode.com/svn/trunk/Spacebuild/
* Click OK. The files should begin to download after a few seconds.
