This article discusses the difference in evaluating group assignments and individual assignments as the workflow might differ slightly.

Grading a group assignment

Whereas with individual assignments Instructors can choose whether to apply the grade in the Grade Book or in the Assignment folder, for Group Assignments where a single grade needs to be applied to all group members, it is required to assign the grade in the Group Assignment Folder.

To add a Group Assignment grade, open the submission in the Assignment folder and add a score to the assignment.  The grade will be applied to all members of the group (for this particular assignment). Underneath you are able to add any comments in the Overall Feedback box. Lastly, you have the option to add additional comments/feedback by adding attachments using the 3 options in the bottom.