Hi.
1) make a mental note of where the # one spark plug wire goes to the distributor (front plug on right side head)
2) Remove the distributor cap ant turn the engine over by hand until the rotor is pointing to #1 spark plug wire AND your timing marks on the front pulley lign up.
3) As accurately as you can, mark the position of the rotor onto the body of the distributor. You can now unbolt the distributor, raise it up about an inch and turn the rotor clockwise about 10 degrees, or one tooth and sit it back down. Now rotate the body of the distributor until your mark sits directly under the rotor. Now check with timing light and tighten down.
You can skip steps 1 & 2 if you are confident, but this allows you to keep track incase you turn the motor with the distributor out.