I bought one years ago, it generally takes about 20 hours practice to be able to confidently ride it, turn and stop, and cope with inclines etc. It's best to do an hour or two a day and then sleep on it.
Stage 1 - saddle under your crotch, get one foot on a pedal at 6 o'clock, push up to sit on the saddle, fall off again.
Stage 2 - as above but put the other foot on the other pedal, lean forward so you think you're about to fall, push the other pedal round to 6 o'clock to move the wheel forward underneath you to rebalance again, come off involuntarily but safely.
Stage 3 - as above but increasing number of pedal turns until you can just keep going.
If you imagine a broom standing upright on your palm - if the head of the broom tips forwards you would then walk forwards to get the rest of the broom underneath it again, that's basically what unicycling is.
Steering is a combination of leaning and turning with your waist. Stopping is putting one pedal downwards and dismounting before you fall off. I never got the hang of pedalling back and forth on the spot.
I would like to try it again now to see if the adage that 'you never forget how to ride a bike' also applies to one wheel.