I will tell you my way, others may have a different way. With engine off plug vacuum advance and turn both screws clockwise until you encounter resistance and then a slight turn and they should be set, going too far can and will damage the screws and possibly the seats. With the vacuum gauge attached to manifold vacuum fire the engine and hopefully you won't have to increase the idle to keep it running. Observe the reading on the vacuum gauge for the highest reading as you adjust the screws one at a time. If you had to increase the idle you will probably be able to adjust each screw clockwise no more than a half turn to get the highest reading. Otherwise you'll go counter clockwise about the same. The more radical the cam the lower the reading and the more the needle tends to fluctuate.