I believe I've written reviews on some of the apps I've purchased in the Microsoft Store in the past, but lately I've been unable to. I cannot for the life of me find where to go on a given app page to write a review. I can read reviews by others, but I can't write my own. There is no link/button to click on to start.
you should be able to leave a rating and review. Make sure you are logged into Microsoft Store, and you downloaded the app. But to leave a review, go to installed apps, find the app and click on the three dots. see below.