If you're managing a number of customers, you may want to separate them into groups. Customer groups allow you to control which of your internal users have access to specific customer accounts and their models.
To add a new customer group, navigate to the Customers tab of your main account, and select Add/manage groups:
Select Create, give your group a name and description, and select which of your internal users should have read and/or write access to the group.
From the same menu, you can move to the Manage tab to modify your groups. You can change group names and access.
Once you have a group set up, you can edit existing customers to the group. Select the pencil icon next to the customer, and select the appropriate group from the drop-down: