Use the straight right after you have set up an opening with your jab.
After establishing your stance, shift your weight to your left leg. Pivot your right (rear) foot so that your toes are pointing forward, while simultaneously delivering a right punch. Remember to push against the floor with your rear foot. (At the very last moment, rotate your fist so that your thumb is facing the floor.)
Pull your hand back on the same plane the punch was thrown. Return your rear foot to its original position-toes pointing between 12 and 2 o'clock.