If submission approval is enabled on an assignment, you may be assigned the task of approving or rejecting assignment submissions.
You'll receive a notification when assignments are ready for your review. You can open the assignment from your notification flag.
You can also see what requires your attention on your dashboard.
Within the course, you can also find which assignments require your review on your mentor dashboard, if enabled.
Lastly, you can find the submissions requiring your review in the gallery.
When you click into an assignment, scroll to the bottom to leave a feedback comment, then click either "Send Back for Revision" or "Approve".