where is settings so I can update my payment information

There is no "Settings" on a Mac. On a Mac it's called System Preferences. To edit your payment method for iCloud, go to Apple Menu->System Preferences-> Apple ID->Media & Purchases->Manage [Account]->Manage Payments.

Or through your account in the Mac App Store App

More details here: link-> Change, add, or remove Apple ID payment methods - Apple Support