This article assumes that your faculty member has created a Turnitin Assignment in Moodle and that you have submitted your work to that assignment. Turnitin has a component called "Feedback Studio" that allows faculty members to provide both summary and in-line comments in reaction to what you have written. Here's how to find those comments:
Scroll down in the course until you find the Turnitin assignment, which will be marked by the (Turnitin assignment) icon. Click on the link for the assignment: