Ok so there's this girl I like she's a 11th grader but I'm terrified to tell her every time I see her I just freeze I see her almost every day and we go to the same church and she does not know I like her (aka I have not shown and signs that makes her think I like her) everyday I'm  thinking about her I know shes the girl for me but I'm too scared to tell her what should I do

Serenade her with the sweet, sweet tones of "Gangnam Style".  "HEY SEXY LADY...OP OP OP OP OPPA GANGNAM STYLE!"

OK seriously now, I think you're a bit too young to date...but not to tell a girl you like her.  Of course you shouldn't go overboard, but if you really like her, just tell her in as natural a way as possible.  Don't think that telling her you like her means that you have to start a relationship (AKA BF/GF) with her.  Make sincere compliments, and she'll love it, though she might not admit it.  If you worry about what she thinks, any relationship you have with her will be strained.  If you truly love her, you can expect love back, but maybe not in the way you might expect.

Well, if you are too scared to tell her, then you cannot necessarily "tell her", now can you? Hmm. Well. You could try getting some of your friends who are friends of hers to leak the information to her. I know that this sort of thing has worked in the past for some of my friends, but it is not a guarantee (nothing is a guarantee). You could also do something elaborate, sort of like how people find interesting ways to ask out their dates for homecoming or prom. You could also just kiss her, and see what happens, if you are a more charismatic person. The odds are though, that if you want anything to happen, you will have to talk to her. It is rough, but that is how it works. If you do not talk to someone, they will ignore your feelings, or just simply stand unknowing. Good luck. 

Practice talking to her.  Say, "Hi." and ask how her day is.  Say you saw her in church.  Easy things like that.  Take a few seconds, say hi, and keep things moving.
Maybe she's pretty but if you have never talked to her you have no idea who she is and what she's like.  Maybe she's really mean.  Maybe she rescues kittens at an animal shelter.

Find out.  Talk to her, say hello, ask her questions about herself.  The only sign that you like someone is by paying attention to them.  There are no other 'signs' people go by.  Engage her and see her reaction.  That is all you need to know.  

Maybe she secretly really likes you and is waiting for you to talk to her.  She doesn't want to approach you because she's not sure you like her either.  Find out and say Hi.

I am not your parent or anything, so I am not going to slap an age on when you are old enough do date someone, however, I think you should start it off nice and easy first, get to know her first and become one of her friends, and to do that you should always treat her with kindness and respect, and once you enter her friend zone, it gets a whole lot easier. You should never go up to a girl that doesn't know you and tell her you like her because it would make it awkward and it would probably creep her out and you don't want to do that. Just a note, you should try to have good hygiene before confronting her, so no bad breath or body odor, smell nice, and from there just be confident and tell her how you feel, it would probably be best to do this in person though because it isn't the same through text. If you are shy, than maybe right a note and slip it in her locker or something, just AVOID texting her. Hopefully this helps you out, and remember to be confident and not rush into things or else it probably won't work out. Good luck man!