Once a unit (we often organize these in terms of weeks) has ended, you will notice that the content is greyed out and collapsed when you return to the coursework area. To review the work in that unit, click on the chevron icon to the far right of that particular unit to expand the view. 

Once the view expands, you may select an assignment to view your work. In the case of a Turnitin assignment, you may need to “Launch the tool” on the subsequent page to review the comments and grades left by your professor.