I hate to say the same thing as everyone else, but...17? late in the game?!, not even close. I am 32 and started an original band last year. Being a musician, means that music is always a part of your life, no matter how old you are. I started playing bass at 10, and drums at 30, and I can tell you it only gets better with age
Now, as far as HOW to do it, here is my process:
1. Determine that you're going to do it no matter what. (persistence is gold)
2. Find creative individuals who can actually play their instruments. Especially a good drummer, and a guitar player that isn't all flash and no substance.
3. Make sure all individuals are on the same page. Define goals, set expectations, develop friendships, ensure all know how to communicate musical ideas. (Theory knowledge etc.)
4. Shut up and play. If you can get a drummer, guitarist, and/or keyboardist, vocalist, kazoo player, etc into a room, and you can just play skillfully, its a win.
5. Record your practices. Worst case scenerio, you end up having something "allright" to listen to later. Best case, you reverse-engineer a beautiful song or riff that came from pure creativity. Freely exchange ideas.
6. Get to know other bands, go to a bunch of local shows (as a band if possible), get to know the scene you'll be playing in, foster relationships with other bands, meet show promoters, owners,etc.
7. Set a firm goal for how many songs you want to do live, write & practice, deconstruct, let everyone have a chance to experiment with the songs.
8. Once you've got an hour worth of material, or whatever your goal is down SOLID, look for gigs.
9. Craft a set list of the songs, and put them in order for maximum crowd effect. Also think about what you will do between songs.
10. Be on time, and play them gigs!
Good luck to you.