There are at least two paths for you to choose from. Instructors can set up and grade with a rubric directly in an Activity (like an assignment) in Moodle OR you can elect to use Turnitin's Feedback Studio feature through Moodle. Turnitin is an assignment type in Moodle widely used for its anti plagiarism tool. Coupled with it is a grading tool called Feedback Studio that allows for rubrics.
The following bundle of resources will assist you with Rubrics:
1) Here is a video tutorial here which shows you the first path - setting up a rubric in a Moodle assignment.
Here are links with supporting documentation on how to get that done:
2) Turnitin 2 Assignment Type - Through Turnitin, you can use a tool called Feedback Studio to make:
- inline comments
- QuickMark comments
- rubric scorecards
- general comments
Rubrics in Turnitin Feedback Studio: