A peer review assignment in Canvas requires students to submit their own assignment online, and also requires them to assess one or more of their classmates' submissions. Faculty can create an assignment requiring peer reviews much like any other assignment, though in addition to requiring a "Submission Type" of Online, you must also enable the checkbox Require peer reviews. This process is explained in more detail in the following Canvas documentation: How do I create a peer review assignment?
One of the decisions you will have to make is whether to have students do peer reviews anonymously so that students do not see the names of the students they are reviewing. If you choose that option, YOU (as the faculty member) will still be able to see who reviewed which submission, though students cannot see who reviewed them, nor can they see the names of the students they are reviewing. Be aware, however, that you will no longer be able to make comments in the file previewing program in Canvas, but will only be able to add general comments in the Comments box if you enable anonymous reviews.
If you use a rubric on an assignment, student reviewers must also type in or click on the appropriate point values in the rubric in addition to adding in comments on the assignment in order for their peer review to be considered complete.
Also, it is difficult for you, as the faculty member, to see exactly how students will be seeing the assignment, since this is one case where the Student View in Canvas will not help you.
Detailed information is available in the attached PDF document.