To add a guest user to a project or group:

  1. First make sure that guest users are enabled for the group or project. Click “Admin Tools” button from the top right menu, go to “Settings” to select “Guest User Settings”
  2. Once “Guest Users” is enabled for your group or project you can add guest users by their email address by choosing “Members” then “Invite Members”.1
  3. Then enter the new guest users’ email addresses into the “Invite by E-mail Address” box.
    1

The guest users you invite will only be able to see the content of the project or group that you invite them to. They will not be able to see communications outside of their enabled groups or projects.

Under General Settings > Invite Setting, the network admin/team admin/team creator can set permission to Guest-users to allow sending invite to the project as well.

Checking the setting allows network-users along with the guest-users inside the team to invite users.