The correct seat height:
Leaning against a wall
Sit comfortably on the seat, with the cranks vertical (pedals in the 6 and 12 position on the clock face).
Wearing flat soled shoes, place your heel on the bottom pedal, and place your other foot in the normal position on the top pedal.
With your heel on the bottom pedal, your leg should be comfotably straight, but you knee should not be “locked out”.
That is the proper seat height for comfortable riding on a bicycle. On a unicycle, it is sometimes a good idea to lower the seat a centimetre or so.
Only lower the seat a lot further if you need to for more technical riding like MUni or trials where you might need to be out of the saddle for a long time.
Most riders find the seat is more comfortable if you tilt it back as far as it will go. Loosen the four nuts and slide the seat forwards, and the front will rise. You can emphasise this by putting a couple of washers betweent he seat and the seat post on the front two saddle bolts.
Wear cycling shorts - and don’t wear underwear. Cycling shorts should be padded, and should have no seams in the wrong places.
Saddle pain comes from three things: pressure, skin stretching and chafing.
Pressure shouldn’t be a problem unless you spend a long time in the saddle. I normally don’t notice pressure problems on rides less than an hour. I have at least once ridden for two hours without a dismount, although that was uncomfortable for the last part of the ride.
Chafing can be reduced by correct choice of shorts, and by positioning yourself carefully on the saddle. You can lubricate with talcum powder, although some people use cornflour as it’s cheaper. there are also specialist products such as the amusingly named “Butt Buttr”, which does what it says on the tin.
Skin stretching. This si not a good description, but I can’t think of a better one. What happens here is that some of your skin is held in position by friction with the saddle, and tehn your weight tries to make the skin slide on the saddle. The effect is for the skin to stretch or “smear”.
When you freemount, start riding and get your rhythm, then stand slightly, then lower yourself carefully onto the saddle, repositioning everything carefully. Put some care into this and you will find you have fewer problems.