Add Customers to Groups

To add customers to groups, click on the Customers tab.
Then in the lower left, click on the Group icon (Image 1).

On the left side of the window will be two columns.  The most left column is the names of your groups.
The other column is the names of your customers.

All you need to do to add customers to groups is to click and drag the customer into the desired group.
Looking at the group, there will be a number next to the group name to show how many customers are in that group.