In the Admin Panel, you need to enable/save the PayFast payment method by navigating to Account → Payment Profile.
Please refer to the attached screenshot for guidance.

 Once the payment method is enabled, customers can add their card details from the Customer Panel by going to Dashboard → Payment Profile.

 After the card details have been added, the customer can make a payment by clicking the Top Up button and entering the desired amount.
Please refer to the attached screenshots for reference.