In Canvas, all group discussions take place in the context of a Group Set, which is a set of individual groups. Like an office filing cabinet that has many drawers, a Group Set contains many groups. When you desire to use groups in your discussion, be sure to create the Groups Set (filing cabinet) and then the groups within the set (drawers). Choose the desired Group Set on the discussion's settings page so Canvas knows how to organize the group discussions. Students will automatically converse with the members of their group when they click the discussion link in Canvas. The instructor can enter each of the group discussions from the discussion's home page.
Read the OAT Groups support page for more information.