Custom payment methods refer to payment methods that are not processed through a payment processor or payment gateway. Custom payment methods are usually manual payment methods like cash on delivery or prepaid payment, etc.
The common settings section:

At the common settings section you can edit the payment method’s name. This will affect the name of the payment method at the storefront. You can also set the protocol mode for the payment method and change the sorting priority and set the payment method to active or not active.
You can also set the payment receiver to help the shop determine if the purchase amount was received by the mall or the vendor.
It is strongly recommended to use the HTTPS protocol payments where sensitive data is send. You should use it, if it’s available for your site.
The payment form title section:

At the payment form title section you can edit the text, that will appear on the payment form , if a customer selects this payment method to pay.
The payment page message section:

At the payment page message section, you can enter a message, e.g. additional information about this payment gateway, that will appear at the payment page, if a customer selects this payment method during checkout. e.g. how the payment will be processed, how the customer needs to proceed to pay, etc.
The thank you page message section:

At the thank you page message section, you can enter a message after the order is processed at the thank you page.
You can enter any message there, that you want, from a simple “thank you for your order” message to additional information about how an order is handled, if a customer chose this payment option, how the customer needs to proceed to pay, etc.
After you entered all your custom payment methods information and made the desired changes, press the “Save Changes” button at the bottom of the page to save your settings.