If you haven't yet been paid for a shop, you can create a PayPal account to receive your payments. This account must have the same email address as your Presto account, because that's the email address we use to pay you. You can also change your payment method to Amazon or Tango Card credit.
To see if you've been paid for a shop, check your shop log. If you've been paid, you will see a line that says "Submitted for payment".
If you've been paid for a shop according to your shop log, PayPal has your payment, but it is unclaimed. You can claim it by creating a PayPal account with the same email address as your Presto account, and verifying your email address. To sign up for a PayPal account, go to http://www.paypal.com.