Here are my suggestions from my experience:

1. To start, use a doorway (as suggested) or a narrow hallway that you can reach the walls with both arms.
2. Wear tennis shoes, not your clip-in cleats, to start/learn.
3. Get a small step stool beside the rollers to mount the bike and to keep one foot on the step stool for initial balance.
4. When mounting the bike on the rollers, lock both brakes with your levers/hands.
5. With the non-stool foot, make sure that you are ready to press down on the crank to get the wheels going. As soon as you start pedaling, lift your other foot onto the pedal.
6. DO NOT LOOK DOWN. Look down ahead 5 to 6 feet. Use your peripheral vision to make sure that you are staying on the rollers and not drifting to the edge.
7. Once you are pedaling, it's not difficult to stay up. "It's like riding a bike". Just be smooth with your pedaling. Don't shift gears at first, just pedal. Shifting will cause you to shift your weight and balance on the bike which it turn will cause the bike to shimmy on the rollers. You'll find the bike is very sensitive to movement and/or shifting weight while on the rollers.
8. To dismount, slow your cadence. Be prepared to put your foot on the stool. As soon as you do or start to move your foot toward the stool, clamp the brakes to stop the wheels. The bike will basically fall toward your dismounting foot and the stool.
9. Be prepared to sweat a lot. It doesn't take long to build up the body heat and the sweat will pour off of you, even in an air conditioned house. Put a large fan in front of the rollers. I would use my rollers on the front porch in 30 to 40 degree days in the winter and would ride in a t-shirt. It felt great.

Good Luck! It's fun, but I could only do 20 - 30 minutes before it got too monotonous for me.

John