What should I do? (I really need a solution)

Hi, I'll introduce myself, i prefer my name to be anonymous,i live in Chile and I'm a 16 year old guy that goes to 11th grade, so here's my story, since i arrived at this school i have been always intrested in this particular girl, she is very pretty and im kind of in love with her, to take note, I don't want to be arrogant but i dont consider myself ugly, I consider myself just a bit over average and the girl that i'm talking about too, so she is in my same class, we go to the same subjects and see each other a lot, we talk a lot too in luch and breaks, sometimes over snapchat, she has been giving me the "signs" and on monday she told me that when we went to a party she was mad because she wanted me to do something, i am a very shy guy, i dont have much personality (without alcohol) and i want to tell her that i love her and have a lot of feelings for her, i dont usually go around forums and stuff but this time i am kind of desperate so if you are still reading i thank you very much, anyways, i dont know how to tell her, i dont want to **** up, what if she says no?, it will ruin our relationship as friends and it will be pretty weird in class because she will know that i really like her, i dont know what to do, i really want to do something about it but i dont have the confidence and personality to do so, please please tell me what can i do, advises, how do i tell her that i love her, i appreciate everybody who just reads this, thank you.

If there is orthography errors, forgive me, english is not my firs language.
thank you again
-an anonymous guy