i have a 91 vw jetta with a 1.8l engine i want to swap the engine but i dont now how to do it or what engine will fit it can some on help me    

well the process is a little more involved than what can be easily expressed  in a post. The easiest swap would be to find a Corrado VR6 and swap everything over on the subframes. You can go crazy and do a 1.8t or even a 2.0t, but that is much more difficult.