So, first thing to do is find top dead centre and then mark or adjust your metal tab to align with the mark on the stator.
So two methods to find TDC:
1. Pop a the plugs out and turn the engine over shining a torch into the bore. TDC is when the piston is at the height of its stroke on the compression stroke
2. A little more accurate. Get a degree wheel (print one off on line) bolt it to the crank bolt on the stator and fashion a pointer so you can read the angles. Get an old spark plug and extend it about an inch. Screw said plug back into the head. Turn the engine (gently) until it hits the stop. Note the angle. Turn the engine all the way back round til hits hits again. Note the angle and split the difference. Turn the engine back round til that split angle shows. That is true TDC. Set your marks to that. Incidentally, the T and F stands for TDC and Fire. Fire being your advance mark.
Use these marks to set your timing whether being points or more up to date electronic ignitions.
Worth grabbing a manual as they give far greater detail than my ramblings.