How to delete your internet history forever in a gigabyte laptop?

well I'm only I freshman and u know how hard highschool is and I'msellingn my laptop to a classmate from school and she has beendestroying my life while since forever so I was wandering if I can delete the things that I entered online permanently because I don't want him looking to what I have in my computer and the history in it thanks by the way I have to give him the laptop tomorrow and however I'll delete it have to be free cause my parents are really uptight and if i tell theme I want to delete computer history they'll think I';ve entered something wrong LOL so please help me delete internet history permanently