I'm a sophmore in high school, and i've been finding my style over the past two years. I think those things are what you find through experimenting with what works for you. I've always loved clothes and shopping, but this year I've just gotten into clothing and fashion a lot more. You have to find your style, which is something that you can only do for yourself. It's not something you should stress about, but you should be comfortable with what you're wearing and enjoy getting dressed and putting together outfits. I love shopping online, and there are lots of websites that give me inspiration. I love online fashion blogs.
For makeup, I'd say that you should start with simplicity. When it's obvious someone is wearing makeup, sometimes it doesn't look good. Mascara, blush, concealer, and foundation if you need it. Use eyeliner if you want, but try not to use too much, unless you want the racoon look (its some people's style).
When you get dressed, make sure you have respect for yourself. A lot of girls show off way too much and while it can be good to show off a little bit of cleavage or leg sometimes, it's not if you're too young or if its too much.
Go to a hair salon and ask them about what different hair cuts would do to your face. Get inspiration from your favorite celebrities (that works for clothes too) and ask about the perm. I would recommend not doing it to yourself.
My favorite store is urban outfitters, and while i do buy things in other places, i always know that i'll be able to find something i know at uo. You'll be able to find a store that you can depend on for a lot of your wardrobe.
If you want to emphasize your long legs, wear shorts or skirts often, or skinny jeans. Over time you will figure out what looks good on you and what are your best colors. Look in magazines like teen vogue (seventeen, nylon, whichever is mostly your style) for inspiration, and find your own style. Wear what makes you happy and comfortable, and you'll look great. I hope i helped!