To make a form available for use within a group, you need to create a shortcut to it.
Only webmasters and those who have access to the form’s settings can do this. This option is found in the navigation bar under Forms.*
Copy the link to the form
Adding a form to a group
Go to the group.
*If you cannot see any forms in the navigation bar or cannot edit the group's page, then this option is not available. Contact the group manager.