A320- need help with auto pilot

hey,i have recently got in to flying airbus a319/a320/a321 which is a change from the 737/757 that i am used to flying. I purchased the pss a320 package but found that my pc can't handle it. I then downloaded the a320 panel by marco spada with the real crt gauges to use until i get my pc updated. The problem is that i cant seem to use the auto pilot. Could someoine please give me a sort of walkthrough of how to load up a flight plan into the fmc and then how to make the auto pilot fly it. Thanx,graham