In 'Manager', select 'CRM' from the left-hand menu. Select the 'Customer groups' tab and click on the 'Create Customer Group' button in the top right-hand corner. Enter the name of the customer group you'd like to create.
Once the group is created, it will appear in your list of customer groups. Click the group name in order to add customers.
From here, click the 'Add Customers' button in the top right-hand corner. A window will open allowing you to search through your customers (retailers). Search the customers that you would like to add and checking the box next to their names as you go.
Once all customers have been selected, click on 'Add' to successfully add them to the customer group.