For example if you are adding a Payment Gateway for onBoard follow the steps below:
Navigate to:
  1. Core > Settings > Payment Settings > Payment Processing
  2. To add the payment gateway information, click the Add New Account button
  3. Select the payment gateway type in the Gateway drop down menu
  4. Mark the Active check box to activate the payment gateway account
  5. Enter the Account Login and Password information for the Account
  6. Select the Credit Card options if any that you will be using
  7. Create a Description for the account (i.e. Contracts)
  8. Click Save