From the products, Tab click on the GROUPS link found at the top right.
To add a GROUP click on the ADD found at the top right.
Assign the GROUP a name.
There are two ways you can assign customers to the Product Groups.
DETAILED: With this option, you can pick the products individually that you would like to add to the product group.
BULK: With this option, you can select the products by category or even Sub Catagory.
On the ASSIGN CUSTOMERS, is the tab is where you would go ahead and pick the customer you would like to assign the group to. Check the box to the left of the customer name to add the customer. Be sure to SAVE your changes.