how can i?

You cant. Unless your parents you give you one under their account.

Some Credit Unions allow 16 year olds to get a 'secured' credit card. This means with a parent you put money in a savings account. You must keep this money as security in the account. Then you get a credit card for the amount usually $300.00
You need to do this for at least a year, but as you are responsible with your credit your limit will increase.
Good luck