First of all, are you in the US? If so, the license is free, although it's $14 to take a test. Your best bet is to pick up a study guide at your local Amateur Radio store. They might still carry them at Radio Shack as well.
Find a local amateur radio operator. (That's the normal name for a "ham.") Do you see anyone with big antennas on their houses near you? Or funny lookin antennas on their cars? Chances are, they're a ham.
Most people like to get started into amateur radio with a 2M FM hand held unit. You can usually get them used for less than $100. It's basically a very good quality walkie talkie, and you should be able to talk all over the city using a repeater system.
The radio in your link, although it doesn't say it, is more than likely a CB radio. It's not the same as a ham radio. Before you buy any equipment, make sure you discuss with a licensed ham if it's the right thing for you.
If you have any questions after this Question is closed, feel free to email or IM me. I am a licensed amateur Extra class operator, and I would be happy to steer you in the right direction or help you find a local 'Elmer.'
Oh yeah, and 15? No problem! There are some hams as young as 6 and 7 years old! I hope my son will be licensed next year at the age of 5. :-D
Check out the links below, and look on their respective pages for new or prospective hams.