In the library, find the clip you want to review. Hover your mouse cursor over it and press the "Review" action to open the Review application. You might have to press the "..." button to reveal the action. 

In grid view, it will look like this:

In list view, it will look like this:

If you want to review multiple clips, select them all in the library, and press the Review icon in the toolbar which appears at the top:

You should now see the Review application:

Download the Review cheat sheet

Download the cheat sheet, print it, and hang it on your wall! Download the Review Cheat Sheet