There are several ways you can assess assignments:

Use built-in annotation tools to mark up submissions using highlighting, free hand drawing, shapes, and associated commenting.
Evaluate anonymized user submissions to remove bias in the grading process.
Evaluate submissions and leave feedback directly on the Submission page.
Evaluate submissions directly within attached rubrics and leave feedback directly on the Submission page.
Evaluate external submissions and leave feedback in an assignment.
Download user submissions and leave feedback within the files, then upload them back into the appropriate assignment so they appear as attachments to each user's submission evaluation.

Watch how to grade assignment submissions

Watch how to grade assignment submissions offline