Hey Claudia. Place your paper negative in the enlarger, emulsion side down, and expose the paper. You'll have to judge the exposure - when I started, I just made test strips. Once you have the exposure determined, then different images and enlargements can be handled just the way you would enlarge negatives. Just be sure your paper negatives do not contain manufacturer printing on the base side.
I use variable contrast paper with my color head.
The reflected light enlargers look very interesting, but I have no room left in the darkroom for a third enlarger!