You should have an account that supports online transactions with PayPal. I dont't know if Pireaus does that but you should have no problem with Alpha Bank.
All you must do is go to whichever bank you want to, ask them if you can create an online account. You will be given a number ( IBAN ) that allows you to do transactions online via either their online page or PayPal.
Someone should correct me if I said something wrong.