Turnitin: Attach a Turnitin external tool to an existing Schoology assignment
To create a Turnitin external tool assignment on Schoology:
Navigate to a course on Schoology.
Click Add Materials.
Select Add Assignment.
Fill out the details of the assignment (name, description, due date, etc). Then click on the external tool icon, pictured as a yellow ruler, below the description box.
Select Turnitin LTI for the Tool Provider, fill out the title of the Turnitin assignment, then click Submit. You can leave the URL blank, consumer key, shared secret, and custom parameters blank.
Open the assignment that you just created and launch the attached Turnitin external tool at the bottom of the page (yellow ruler icon titled "Essay" in the example below).
Click the gear button in the upper right, then set the Start Date to when you want students to begin submitting to Turnitin, and set the Due Date for when you want students to complete the assignment by. Check Optional Settings to make adjustments on late submissions, saved settings, etc. Click Submit.