Peer review is where you score another learner's assignment against the same rubric an instructor would use. Your inbox of work to review is at uni.xyz/courses/reviews, or Peer reviews in the courses app sidebar. You need to be signed in.
You will not get anything to review on most courses. Peer review only runs on assignments the author set to peer grading, and it starts when work is submitted, not when you enrol.
You are matched when you submit, not before
Submitting a peer-graded assignment triggers the matching, and it runs in both directions at once. You are given up to N other submissions to review, and up to N reviewers are put on yours. N is the number of reviews the author requires. Work with the fewest reviewers already on it is picked first, so the load spreads evenly, and you are never given your own submission to score.
If you are the first to submit there is nobody to match you with. Your inbox stays empty and reviewers arrive on your work as other people submit. That is expected and it resolves itself.
If you joined through a class code, your pool is your own cohort. Learners with no cohort draw from everyone else who has submitted.
It is blind in both directions
You never see whose work you are reviewing. The submission arrives as its contents and nothing else: a link, an essay, files, or a project shown as a plain number rather than a link, so there is no way to look the author up. They never see who reviewed them either, and the written feedback reaches them without your name on it.
Scoring a submission
Open an item and score every criterion on the rubric. All of them: a partly scored review will not submit, and the server refuses it as well as the page. Written feedback is optional. Once you submit, the item is marked done and leaves your inbox.
How the reviews become a grade
On peer aggregate, the grade is the median of the peer scores, and there is none at all until the required number has arrived. On blended, that median is mixed with the instructor's mark at the weight the author set, and both parts have to exist first.
This is why a peer-graded assignment can sit unmarked for a while. It is waiting on other learners rather than on a marker, and the wait ends when enough of them review.