Well, good luck! For the first few minutes, if you don't have training wheels, just sit on the saddle and scoot yourself along by pushing with your feet. Or get a friend to run along behind you, pushing. You'll need to learn the trick of going in a straight line, holding your arms steady. If you can find a very gentle slope, start at the top and just roll down (rest your feet on the pedals) several times until you're used to the balencing. When you're fine with balencing when the bike is going straight, learn to pedal while balencing and going straight. When you're fine with going straight and pedalling along, try setting yourself up an obstacle course (a few random things in a nice flat carpark, for example), and start learning to steer. It can take a while to learn the movements, pointing your arms at where you want to go. When you're confident that you can pedal along without falling off, and steer around things, try putting on a bit of speed. The faster you go, the easier it is to balence. If you're going fast enough, you can steer just by leaning into the curves and shifting your weight.
The next thing after that is pretty tricky: learning to ride safely around other road users. You need to be able to keep going straight and look back over your shoulder, hold one arm out to signal a turn, etc. At first, just practice looking around you and keeping going straight, rather than at what you're looking at. Then, try a glance at 90 degrees over your left shoulder (assuming you drive on the right), back at the traffic trying to overtake you. Try to look for just a whole second without deviating from your course. It's hard! When you can look around safely, try cycling along with just one hand on the handlebars, without changing speed or direction. When you can do that fine, try cycling along for a long way with one arm out. Try it for both arms (not at the same time, obviously).
And, most importantly for your safety: find out about the rules of the road for cycling! If you're expected to give a signal before turning, doing so may stop you being driven over by some jerk in a big car. Learn the signals for "turn left", "turn right", "stop" etc, and make sure you can make them. On the road, the only thing more vulnarable than a cyclist is a pedestrian. Develop some paranoia and awareness of where all those dangerous fast hunks of metal are.
The best way of combining the last two paragraphs, once you've learned more or less how to ride, is to take a cycling proficiency class. These might even be free: they teach you a lot of useful stuff, and you get a pretty certificate. Local schools might be able to help you with finding out about those.