When you go to WalMart or something similar, you put money onto the account, and you get a temporary credit card number after you activate it on their website. It takes about 5-7 days for the real card to come, but you can still use the temporary one just fine. If your funds aren't on there, someone owes you some money then.
Edit: By the way you have to be at least 16 to have a debit card, otherwise your parents are about the only other option.