First you have to have a savings account at a bank. Did you parents help you get one? I put part of my money from gifts into my account a few times a year. I also add money when I work some jobs around the house or for friends. I like to pet sit a dog, and help with plants outside.
The bank has a small paper to fill out. You can find them on the desk before you get on line. Pick the one that says deposit on it. You have to write the date and your name and the account number and the amount. The account number comes from your booklet that the bank gives you when you make an account.
When it is your turn, you give the bank person the deposit slip and your money. They enter it for the computer and give you a receipt. Then you can add the amount to your bank account book and total it up.
I was really happy to make my deposit at the bank. It made me feel more grown-up. You can do it, too.