Referring to the picture below, you must now choose how you are going to make payment via PayPal.
Your choices are: [NOTE: you don't need a PayPal account!]

1. Select to make payment via credit card, without a PayPal account - Click the Continue link just above the images of the credit cards.
2. Sign into YOUR PayPal account; where you can use your PayPal balance or your Credit Card

Having selected to make payment with a Credit Card (not via a PayPal account) you will see the screen below. Fill in the information as requested and then click the Review Order and Continue button

Just sign into PayPal