As soon as you create your assignment, you can add the document samples on the main Assignment Dashboard screen. You'll see the "Manage Instructor Documents" button (pictured below) where you can upload your documents.
You'll categorize these documents as "strong" or "weak," while students won't see these categorizations.
Students will use the assignment rubric to rate and review all of the instructor documents, so remember to take time to set up and manage your rubric.
Students will receive a reviewing grade (including both accuracy and helpfulness, if there is a feedback phase enabled), as well as a task grade for completing all parts of the assignment. The reviewing grade and task grade are combined to produce the Overall grade for the assignment.