Hi morethansilver and welcome to APUG. It sounds like the technique you are trying to do is combination printing. I don't know how experienced you are with darkroom printing, but that can be quite difficult to do, often involving the use of more than one enlarger and masking techniques. You may find it easier to start with sandwich printing, where you combine two or more negatives together in the same enlarger. This can work well where one of them is a silhouette. There are plenty of books describing this and combination printing techniques. Try the Darkroom Handbook by Michael Langford. Good luck.