https://www.reddit.com/r/personalfinance/wiki/teachme#wiki_banking

Go to a local bank or credit union near where you live (a credit union is basically just a customer-owned nonprofit version of a bank). Many of them offer free accounts for students. You will probably need to have a parent or guardian as a joint owner of the account since you are still a minor. Once you turn 18 you can go back and open your own individual account, transfer the money over, and close the joint one.

Don't forget you may also owe taxes on the money you earn, depending on the total amount.