JUMPING A BMX OR MOUNTAIN BIKE (or a motorcycle) uses the same row and anti-row movements you develop on your RipRow.
Tips and video:
To fly high, row through the lip. As soon as the rear wheel leaves the ground, slowly anti-row through the air. This gives you a high trajectory.
To fly low, row more powerfully into the bottom of the lip. As soon as the front wheel leaves the ground, quickly anti-row. This gives you a low trajectory.
Practice both styles of jumping, both on your RipRow and on your bike. The more you expand both ends of the range, the easier it'll be to handle a wide variety of jumps and speeds.
Have fun out there!