I'm guessing that because you're asking here, you don't have any family members able to get you started? (That's okay if you don't. I didn't, either. I'm the only person in my family that sews, and I started by experimenting with a couple of very old machines inherited from a deceased grandmother.)
Do you have any fabric stores in your area, like Joann or Hancock? Many fabric stores offer sewing classes, so you and your parent(s) can call around to your local fabric stores and ask. Sometimes they have classes geared toward people your age, or instructors who can tutor you one-on-one.
You can also look around for sewing machine specialty shops in your area. These are small businesses that sell nothing but sewing machines and sewing supplies. (And, strangely, vacuum cleaners.) They usually offer lots of sewing classes every month, and if you don't have a sewing machine available to use or borrow, they'll probably have a lesson model around that you can practice with.
Getting a basic sewing kit is also a good idea. You can practice with hand-sewing. There are lots of simple beginner project books out there, and there's lots of ideas online, too. I started by handsewing trims onto bought clothing, or machine sewing very basic things like sashes. This is my suggestion for a starter hand-sewing kit:
- angled fabric scissors (they look like this
- they are angled, not straight, and they're sharper than paper-cutting scissors)
- thread scissors or snippers
- a pin cushion
- ball-headed pins
- hand-sewing needles
- a measuring tape