Payment Gateways authorize credit or debit card payments for orders placed on the store. You will need to have an account setup with a payment gateway provider service to utilize the feature.
Go to Site Settings > Settings
Scroll down the page to the Payment Gateways section.
Currently Authorize.Net and PayPal are services available for payment gateway integration.
Once the account information for the payment gateway service has been entered, scroll to the bottom of the page and click Submit.
You are now ready to accept electronic payments on your store!