Where can I find tutorial how to use turnitin?
Turnitin has a User Guides page here User Guides - Guides.turnitin.com
And below are links to a couple more pages you may find helpful from that site.
It also might be worth checking with any of your local support people. There are currently two different ways that TurnItIn can be integrated with Canvas so checking with them might help you get the specific guidance.
Whatever Turnitin have done, none of the previous links to their docs work. They all go to the Turnitin Help landing page. What were they thinking?
Agreed, it sure seems different now. Here's a possible starting point for Canvas users:
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