It is much easier to learn how to work on bikes when one already has basic mechanical skills such has how to use tools properly, torque and lubrication basics.
Basic mechanical skills transfer from discipline to discipline and can be acquired in many different ways.
Learn to work on cars, washing machines or anything you can get your hands on.
Hang out with friends who work on stuff such as motorcycles or lawnmowers.
Any experience at all is valuable.
-Tim-