For the top I did things a bit different since both the front and the back of the top cushion will be visible.
I first covered the front of the cushion like I did the seat of the chair. Once that was done I took another piece of fabric and layed it over the back. I folded under the sides and ironed the edges to make them crisp and clean looking for when I stapled.
I decided to take the hideous piece of plastic off the chair part too. It just looked so cheap and nasty.