How to start a clothing brand?

Cuz recently I have really wanted to, but I'm only thirteen, I have no money, and I don't know about business. But I have a logo and kind of a sense of modern fashion. What I thought of though is if I could get in touch with famous people and ask what they think if I designed some clothes and see if they'd wear it, because if I could get money invested and make something a public figure would wear since people are like sheep when they see their idol wearing the brand they'll want it, and then everyone rushes to go get it. And I love clothes. The above idea might be unrealistic though because I don't think I could easily contact a famous person.

It's going to take a lot of work. You need to understand garment construction/sewing, fabric, branding and marketing, merchandising, finance, business management, etc. Learn EVERYTHING you can about the industry, and the players in the game.

If there are sewing, art (you need to learn to sketch very well), or business classes at your school, think about taking them.

Also search "fashion school" to learn about some of the programs out there. It's going to take some training.

Search "start a clothing brand" and you'll get tons of info, including:
http://www.wikihow.com/Start-a-Clothing-Line
http://addicted2success.com/success-advice/top-10-tips-on-starting-your-own-successful-clothing-line/

While you're preparing for school, training, etc, think about what's unique about what you'll design. A brand needs to be unique, so think about what's special about your design vision.

You can also start with a t-shirt line now. Check out http://www.cafepress.com/ and other sites like it. You can market your designs to people you know and online through their site, and they'll print the shirts, etc. one-by-one as people pay you with their order. You could also check out etsy.com and maybe sell there as well.

Good luck!