The way to learn balance on a bent is the same way you would on an upright, except you probably don't have to remove the pedals. The process is called 'draising,' (named after Baron Von Draise's pedal-less forerunner to the bicycle,) and it involves sitting on the bike and pushing with your feet. At first you walk it, and gradually progress to longer and longer strides. When you can push hard and sit back in the seat, coasting until you lose your speed, then you're ready for using the pedals.