Within your distribution portal (YOUR MUSIC > Distribution > Go to distribution):
Go to your 'Account settings' by clicking on the icon at the top-left corner (the Family in Music logo within the navigation bar).
Click o the gear icon ⚙️.
Select the 'Payee settings' tab.
Scroll down to 'Payment method'. Click on it and a drop-down menu will display.
Select Paypal and introduce the email associated with your Paypal account.