Open eBay App and log in to your account.

On the homepage or the bottom navigation bar, find and click the "My eBay" option.

On the "My eBay" page, find and click the "Settings" option.

On the settings page, find and click the "Account" option.

On the account page, find and click the "Payment Address" option.

On the payment address page, you can choose to add a new payment address or edit an existing payment address.

If you want to add a new payment address, click the "Add Address" button and fill in the corresponding information, including country/region, name, street address, city, state/province, zip code and phone number.

If you want to edit an existing payment address, find the address to be edited and click the corresponding edit button to modify it.

After filling in or editing the payment address, click the Save or Confirm button to save the changes.