How to fuse clock setting in an AT Mega 8535 micro-controller?

I am new to this micro-controller business.
I am using AT Mega 8535 micro-controller and using a 8.000 MHz external crystal oscillator.
I wish to know how to fuse the clock settings in the micro-controller.
I am using CodeVision AVR Complier Evaluation Copy and TopWin Ver. 6 Programmer.

You should have AVRStudio installed as well.