In order to create a hinged top style bench, you will need to reassign the Sides in the Side tab so that you can make the top into a face, and door (and hinge operations) can be added. You will want to go into the Product Editor, select the Shape tab, and then choose the Side tab. You will click Edit Side Shape, and click Yes to confirming that top or front shaping information will be lost.
When the shape editor pops up, you can click Ok as you are not actually changing the shape. From there you will have the options to click on the different sides and change the type. You will want to change the top to a face type.
Click on the Face tab, select the new Face (Face 2 in this case). You can add a door, and change the hinge to top.
Please see the video below: