Go to your company panel, then to Service Types, add a new service (add rate button) or select the one that is already active. Go to 'Payment methods' and enable the option of payments with credit and debit card.
Download the passenger app and add a card with the next credentials:
Card #: 4111 1111 1111 1111
Exp. date: any date
CSC or CVV: Any 3 digits.
Same demo card you can add in driver app for the demo driver top ups and more.