When you add a site to a site group, the site cannot already belong to the site group as only one instance of a site can exist in a site group. If the site group contains shareables, the site cannot belong to any other site groups that contain the same shareables.
Open the Business Control Center.
Select Site Administration.
Select the Site Assets link.
Enter the name of a project and click Continue.
Select the site group to edit.
Click the + icon from the Actions menu and select Edit.
The Site Group panel appears.
Select the sites that will be part of the site group by clicking and dragging the site into the pane, or by clicking the Select button and selecting the sites.
Click Save to save the site group.
