Student: How do I submit a paper to a Canvas Assignment that uses Turnitin?
Click "Assignments"

Note: The Assignment might be linked from a different tool such as the Modules tool or the Pages tool.
Click on the name of the assignment

This displays the assignment instructions.
Click "Upload Submission"

This displays a Submit File panel
Enter the name of the paper, then click "Select a file to upload"

This displays your computer's file locator.
Locate the file on your computer, select it, then click "Open" (or "Choose")

This lists the file on the submission form.
Click "Continue"

Click "Accept Submission & Save"

This submits the paper and displays your submission details on the Assignment page.
Example:

NOTE: The Turnitin interface will not allow a student to resubmit to Turnitin on the same assignment.