Advance is controlled by the tension of the advance springs against the mass of the advance weights. As speed increases, the weights get heavier and the springs stretch, and the cam turns and the advance builds and son on. Advance spring tension limits the max advance. Easy to change spring tension, might find springs at hardware.
If you mean how to set the base timing (timing at idle) base is usually 8 - 20* on most automotive engines. Set it to fire a bit before TDC and change it either way. Retard (toward TDC) will slow the engine, advanced will increase the speed. Retard takes more fuel.
A timing light is vital to make sure the timing between cylinder pairs is the same, it can run badly (like carbs out of synch) if the balance is off.