How to propose to crush ? (Read post please)

So I have a crush on this girl since 2 years(class 11 now in 12) I have not really talked to her except simple things like asking her coaching, what's the time and all. I feel quite shy talking to her and can't even maintain eye contact, but I often find myself just watching her. I'm planning to propose her on the last day of boards, please guide me about all this