I am a new user of Ubuntu, and to be honest completly new to the whole linux scene. I'm looking to add more brushes to my GIMP program, but I don't know how.
To add brushes to Gimp after you have downloaded them and/or opened your Zip file you need to move them to your brush folder(usually found here: C:\Documents and Settings\myusername.gimp-2.6\brushes). After you have done that you simply need to hit refresh in your brush dialog box.
You could read this which also tutorial on installing brushes in Gimp.