Need to ask girl out

I am graduating high school in 4 days and i recently got interested in girl who is freshman she is cute beautiful but i didnt talk to her yet,she is always with her friends and when she pass by me she almost always look at me,but not becouse i am goergus witch i am certenly not but becouse wholle school know our class and specialy me becouse we are always smiling and having fun.So i am not pretty not even fit,but not fat and i am short(168cm)😁.I really like the girl but I dont know to go to talk to her ,i think i know what to say and everithing and i am not even much nervous ,maybe becouse i never had a girlfiend....I just dont know what is wrong with me.