Firstly, there is no age limit at all. Provided you have an understanding of radio and can pass the test, you can become a HAM. The youngest HAM operator I’m currently aware of is an 8 year old girl in Florida. (Images of her working are on youtube).
The easiest way is to contact us, and we can get you started. Effectively you need to sit a small test (which you could learn the answers to in a few hours by reading a small book) that involves both written and practical examples to get your foundation license.
However, if you would like to try it out first, many of our members would be more than willing to show you the ropes, and even let you operate the equipment to have a play. (Provided their station license allows for this, which most do.)