You have to be admin of the group to do the following changes

The group admin can view and share the group access code. This enables every Sdui member of the school to join this group by entering the code.

Each group has its own group access code. To view this access code, open "My Groups" via the drop-down menu in the top right corner of the header. Click on the desired group from the group overview.

At this point you should be able to see the group's list of members. In this view, select the "Settings" tab.

Here you can see the access code for the group. You can also share it by email.