Credit Card are enabled by default if the seller is able to accept credit cards.
For a seller, ability to accept credit card payments depends on country and region. We need to be able to transfer money to the sellers for items sold through Credit Cards, and there are certain rules and regulations regarding money transfers. At this time, only sellers in the USA can accept credit cards.
Also due to regulations, our payment processor does automatic verifications to determine eligibility. If you are a seller based in the USA, and you can't accept Credit Card, this is due to your profile is incomplete or inaccurate and have failed the automatic verification of our processor (btw, our processor is part of the Paypal family and the same one used by Airbnb and Uber). Please contact us at email@example.com, we'll take action to help you address the issue.
However, anyone and anywhere can list something for sale and accept cash on pick-up.