Once you have a PayPal Credit account, when you check out with PayPal you’ll have the option to select PayPal Credit as your payment method. You can also set PayPal Credit as your default payment source. That way, as long as you have available credit in your PayPal Credit account, every purchase you make with PayPal uses your PayPal Credit account as the payment method. Additionally, some merchants have a PayPal Credit option at checkout. If they do, you can simply choose that option.