I bought one, on a whim, a long time ago, around 1991 I think
(I'd actually set out to buy a computer: in those days you had to go to a proper 'computer shop' to buy a computer; but I passed a magicians' prop shop, which had unicycles in the window, on the way to the computer shop).
Anyway I came home with computer
and a unicycle... It took me about a week to get some sort of mastery of it (the unicycle I mean). At the end I could do about 100 yards or so, on a firm level surface. Since then, I've totally 'lost it' - can't go so much as a yard, now: but maybe with a bit of practice it could come back ???
Find a place with smooth tarmac or concrete to learn on. Don't try on a slope, on uneven ground, gravel, or grass. I used my paved patio and I found even the cracks between the slabs troublesome, at first! Have somewhere where you can clutch a wall or something with
each hand. I have a place at the edge of the patio where the house wall and a convenient garden wall are about 1 metre apart. You can of course get friends to hold your hands, but it gets tediously boring as you work at it for hours on end, perhaps a good way to turn a friend into an ex-friend...
You start with the saddle (which should be set with the front somewhat higher than the rear - same for ladies and gents BTW) under your posterior, the wheel a bit forward of you. Decide which foot you're going to start off with (for me it was the right), have the pedal on that side just aft of vertically up. Put your foot on the pedal, pressing down will force the wheel to move directly underneath you. At the same time put the other foot on the other pedal.
You should now be in a 'locked' position, still holding onto the walls, with both pedals horizontal and you can control the wheel fore and aft with slight foot movements. Practice getting the 'feel' of the thing.
Now you're ready to launch yourself into space! Let go both walls as you
lean slightly forward and give the pedals a half turn to the next 'lock' position. If you do it right, you will still be upright after the half turn, then you will lose balance and fall off, the unicycle shooting off either forwards or backwards. Be prepared for this, many times!
The next advance is to try and do a full turn before 'locking'. Then 1½ turns. Then two turns. Away you go! The next step is up to you!
Happy unicycling!