PayPal allows a few payments by card as a guest but at some point will require an account be opened.
Its best to open from the get-go. Claims for items not received are difficult if paid as a guest. Take a few days to confirm the card.
"When you link your card to your account by authorizing PayPal to charge a small amount, PayPal generates a unique random code which displays on your card statement. Only the legitimate owner of the card has access to the statement. For this reason, this process limits the risk connected with stolen credit cards and fake identities"
Enter code and ready to go. PP refunds the small charge at first transaction.