How do I update my subscription payment information using PayPal?

You must connect directly to PayPal:

From your PayPal app, here's how to update your card information:

1. Tap the Settings icon at the top right.
2. Select Banks and Cards.
3. Select the card that needs to be updated and tap Edit.

From your computer, here's how:

1. Click Wallet at the top of the page.
2. Click the card you wish to update.
3. Click Edit.
4. Fill in the updated information, and then click Save.

Note: each time you add a card or update the information, the equivalent of US$ 1.00 is blocked on the card in order to verify the validity. This is not an actual charge and the amount will be released after a short time. If, after 30 days, you still see this item, please contact your card issuer.

Source : https://www.paypal.com/us/smarthelp/article/how-do-i-link,-remove,-or-change-a-credit-card-or-prepaid-card-faq1457