If you haven't yet been paid for a shop, you can simply add your Presto account's email address to your PayPal account. Please see PayPal technical support for details.
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 already been paid for a shop via PayPal according to your shop log, but your PayPal account is using a different email, PayPal has your payment, but it is unclaimed. To claim the funds, simply add your Insta-Shopper email address to your PayPal account. If you have received an email from PayPal (sent to your Presto email address) notifying you of the payment, and you're logged on to your PayPal account, you can usually claim the payment (AND add your Presto email to your PayPal account) by simply clicking the link in the notification email. Otherwise, please contact PayPal technical support for assistance in adding the second email to your PayPal account and claiming your funds.