Drum loops
If you are worried about copywrite infringment, you can create drums with your voice and then use notch filters in cooledit to make them sound unbelievably real (with a lot of patience). lol
Downloading some drum samples is a better option for quality and variety. I find the best way to use drums is to insert your drum sample (wav file) on the various snapshot points of the timeline. The trick is to change your timeline from showing a time to "bars and beats". You'll need to turn snap to frames on as well. This can all be done by right clicking the timeline.
You can loop your inserted drum sound (or drum loop) in two ways. When you right click your drum sample, you can either choose "loop properties" or "loop duplicate".
Loop properties can be understood more by using the help menu. It's a very powerful part of cooledit, however I've found that it has a weird glitch where the loop stops on some wave files.
Loop duplicate is easy to use. The only catch is that you'll need to make sure your wave selection is spaced out to the correct bpm or your drums will be out of time to say the least.
You can always put your percussion in later if you choose to use the metronome. This section on the bottom right is also used to set your bpm setting (beats per minute).
I hope I've helped.
Mike