It's easy, so you've got Steam installed, that's the first step.
2. You've got the Source SDK 2007 from Library -> Tools.
This will create a sourcemods folder in your Steam/steamapps folder. Close Steam.
3. The GoldenEye Source installer (the file should be just below 900 Mb, like 888 Mb or something) will find your sourcemods folder and ask you if you want to install there - just click okay then.
If you prefer to use the .zip-file you might extract it to said folder, that's just about what the .exe-file does (additionally keeping your achievements).
4. Open Steam - select Library -> Games, it should be listed there, so you can exectute it from there or create shortcuts to your desktop.
5. Please familiarize yourself with the search function of these forums, how to install the mod is described like 10k times around here.
