There are actually 3 ways to learn. So the first way will be learning by using a bicycle with 2 supporting wheels. Yea, I know that is a 5-years old kid method. If you think that it is a bit too childish, may be you can go for option 2. Without the 2 supporting wheels, but you must have both of your feet on the ground to learn how to balance. Slowly take up your feet and pedal the bicycle. This is some how tougher and it may take up more time as compared to option 1.
And the last option actually requires some other people to be with you. Please make sure that this person has good stamina because it requires your partner to run with you. Besides, this people will help and prevent you from falling to the ground and injure yourself badly. So, the last option actually requires you to have your feet on the pedals and cycle your way through the learning process. Your partner doesn't need to hold the handling bar, he or she just need to hold you only!
If you are really an amateur, please make sure you have your head gear and some protections for your elbows and knees.Remember! Don't give up easily!
Enjoy and have a nice day...