Assignments can be set up in Course Site so that students can submit, and be graded, individually or as a group.
To allow students to submit as a group, change the "Students submit in groups" option in Group submission settings to "Yes."
This setting will enable 1 student to submit a file for the entire group. An instructor can then grade and offer feedback that will be distributed to all group members. If needed, the instructor can give a different grade/feedback to respective students.
Note: If a student is a member of multiple groups (for example, the student has been added to a section group as well as a working group), the "Grouping for student groups" choice under Group submissions settings must be set appropriately. If the grouping is not set up, the first submission will be added to the "default group." Which means that assignment will be added for each student in the class. A grouping is simply a collection of groups.