When creating a group, you can select Enable external access
to turn a community group into a place where standard users can invite external contributors
to extend their communication and collaboration to the outside world.
To create a group with external access:
Click > Group.
On the Create group page, enter the group name and
Select Private or Private > Unlisted for the group type.
External groups are limited to Private or Private: Unlisted groups to help
protect community information.
Select Externally Accessible to allow external
contributors to be invited to and join the group. Externally Accessible groups
must be private or secret (also known as Private: Unlisted). You may not see this option if it's not enabled for your community.
Click Advanced for more options.
Click Create Group.
If you see the Invite People to Join dialog box, then
add a few users who you want to invite to the group, and click Send
To manage group features and select the storage provider, select gear icon > Configure activity page.
Click the gear icon in the Enabled Features and Content Types tile.
Select or clear features for the group.
People will be able to create the kinds of things you select.
If available, you can select a storage provider for storing your uploaded files.
The group is created and the user you invited can start
using the group.