In Canvas, there is no concept of storage folders for assignments. In the SpeedGrader sidebar, you can see the details of a student's submission. Assignments.
You access file submissions via SpeedGrader. For compatible file types, SpeedGrader will open the document within your browser, where you can annotate/comment directly.
You can download all student submissions for an assignment.
You can check the submission status of an assignment using SpeedGrader or New Analytics.