The following instructions explain how to apply a rubric to your assignment:
Open up the assignment so that you can see the Turnitin interface, as seen below.
Click on the Turnitin "Settings" button.
Click on the "Optional Settings" link and the menu will expand.
Scroll down and find the "Attach a rubric" setting and click on the check box.
Click on the drop down menu, which currently says "No rubric", to see the list of rubrics available.
Click on the rubric you would like to apply to your assignment, you should be able to choose the Generic Assessment Criteria for Foundation, Undergraduate or Postgraduate level.
Once you have selected a rubric the option should display in the settings.
Scroll down to the end of the Turnitin settings and click the "Submit" button to save the changes you have made.