To add fabrics to a group:
In the Fabrics section, drag the fabric to the group. As you hover over the group, the group icon displays as in the following image.
Drag to Group to add the fabric to the group.A group can have two, three, or more fabrics. To add artwork to a fabric group, you must add it as an all over print. You cannot drag artwork into a fabric group.
For more information, refer to Allover Print.