You can access your closed reviews from Your Reviews tab. Under Previous reviews, you will see all your old reviews which you can open up.
If you're a manager and need to see a team member's closed reviews, you can go to Your Team tab and click on the person's name. Once on their profile, go to their Reviews tab and under Previous reviews, you will see all their old reviews which you can open up.
If you're an admin/moderator and need to view someone's closed reviews, you can search for their name in the search bar and then follow the same steps as above once on their profile.