That is as good a way to get introduced to bicycles as any. Get your hands dirty!
This first order of business is to establish what you got. Measure the rear drop out spacing:

It's either 126mm or 130mm. This will determine what type of drive train you could run.

The next thing is to see what stem arrangement you have. Threaded fork and Quill stem like this?


Or threadless fork and threadless stem?


It's easy to tell the two apart on a bare frame. Does the fork steerer have threads on it? If it's a threadless fork, then you need to measure the diameter to see if it's 1" or 1 1/8".

Once you have the above information, report back, and we'll go on from there. Then you can go shopping for parts.