You can view work submitted by one student or download an entire class's submissions all at once.
Viewing the work of one student
Step 1: Select your student's class from the side menu.
Step 2: Click on the 'students' tab. Find the student you are interested in and click on the 'see more details' button. It is in the same row as their name.
Step 3: Go to the activity that they have submitted work for. Click the download icon.
Viewing the work of an entire class
Step 1: Select the class you are interested in from the side menu.
Step 2: Go to the activity that your class has submitted work for. Click "Download All". This will download a zip file that contains all the submitted work from each student.
Note: This only works for activities that have been set to require a submission from students.