Once installed, navigate to System > Configuration > Catalog > Category Reviews and expand the Category Reviews Settings (as per below). Once expanded, you can then define how and where you would like the category reviews to be displayed. 
One to pay close attention to here is whether you want the category reviews to appear by default. If you select No here, but would like Category Reviews to appear on only certain categories, you can turn these reviews on and off in the Manage Categories screen by navigating into the categories General tab (as per below).