How do I access Turnitin submissions from Summer 2016 and before?

If you used Turnitin through MyUCLA, you will need to login to https://turnitin.com/ to access old student submissions. UCLA has created Turnitin accounts for instructors so you will be able to access Turnitin.com by resetting your password.

Go to https://turnitin.com/
Click Login in the upper right hand corner
Click Reset password
Enter your UCLA email address (official email address in the UCLA directory) and last name
Answer the Security question or click Forgot your answer? to receive a password reset email.
Once you have reset your password, log into Turnitin.com to view your past assignments.

(thanks to Peter Blase for directing me to this information)