To get started processing credit cards with your merchant account for GoPayment, you will need to set yourself and/or your employees up as GoPayment users. To do this, log in to the Merchant Service Center, click "Manage merchant account", and then "Manage GoPayment". Select the "Add User" button and follow the instructions to get the GoPayment user set up. Additional instructions can be found in the Resource Center after you log into the Merchant Service Center or contact support if you need assistance. Log in.