You have several options, and I'll list a few:
-You should have an application called file-roller that is available on most fedora core 3 installs (I don't know what you did/did not install). It handles most compressed formats and is pretty self explanatory
-You also have the command "tar" from the console, if the file is a tar (most compressed linux stuff is). Type "man tar" for more information, or go to the manpages section of this website and search for it.
-My favourite: open up konqueror, navigate to the directory containing your file in question. Right click on the file and click "extract to" then "here."
Let me know if you have additional questions. Without any more information from you, that is as specific as I can be.
Enjoy Fedora! Great system...