Go to your group's page. Select the ‘More’ button and choose the ‘Edit Group’ option.
In the Membership Approval section, select one of two options who will have control over the pending member requests.
Members and Admin
Add the question and select the 'Edit Group' button.
If you want to create a new group and have a question with it for new members, simply select the ‘Create Group’ button on the Group Hub page.
Your question will be displayed when users click ‘Join’ to your Group. Non-members need to submit an answer before their request to join will be submitted. You will see the answers to your Group Question in the Pending Member Request section.