If you don't know how to set the timing I'll give you a method of roughly tuning it. Underneath the distributor is a circular clamp, that secures the position of the distributor once the timing is correctly set and I expect it's this clamp that's somehow become loose in the past. Once you have the engine ticking over s-l-o-w-l-y rotate the distributor one way and then the other; you'll find the speed of the engine will increase. By trial and error (!) you'll arrive at a point where the engine is happy. At this point tighten up the clamp that secures the distributor at this position.
If you need more help, or you cannot make the engine run, I'll suggest an alternative method of fixing the timing.