BookingCentral integrates with the Authorize.net payment processor. In order to take payments for your bookings, you will need to set up an account with Authorize.net. You can work with your bank or existing payment provider to get information about how to connect to Authorize.net as a gateway. Or, you can find more details about how to set up an Authorize.net account here: https://www.authorize.net.
Once you get setup and approved for an Authorize.net account, you can easily integrate the information into your account.
To do so, navigate to Settings - Configuration - Payments.
Select Connect to Authorize.net.
When prompted, enter the API Login ID and Transaction Key that you've obtained from your Authorize.net account. Instructions on how to access this information is included in the link here: https://support.authorize.net/s/article/How-do-I-obtain-my-API-Login-ID-and-Transaction-Key.
When finished, hit Save at the bottom of the Payments page in BookingCentral.