engine timing for a 92 camaro

i recently blew my 92 3.1 v6 engine in my camaro and had a junk yard engine installed. it's either a 92 firebird or camaro engine, and i cant seem to get a good idle. when i start it the idle jumps up and down, the engine light comes on and when i put it in gear it dies. i figure the timing is way off, i'm hoping it's that simple, but it may be more complex than that. used a light and it read that it was off 10 points. i put new spark plugs in it, seemed to help a little but not much. how can i significantly adjust my timing? i know i have to mess with the distributer but what do i have to do with it?