There is a third revision to the GtkRadiant installation guide. This will be used for 0.6 and later, I also even made a video tutorial for it. The new tutorial is located here, while the old tutorial, which you shouldn’t use, is located here.
So, if you don’t have the new media, I suggest you don’t map just yet, and even then I don’t suggest it because you’ll just get confused and stuff, just wait till the release of 0.6 and everything should be fine.