Start at the front and stretch it tight working your way down the sides alternating back and forth. Just a couple of inches at a time. Stop and smooth any wrinkles as you go along. You've got the right idea and it will look really good once you get it stretched taut. I've done some car seats and boat benches and for me the real trick is to work slow and check progress every staple or two.
-------------------- A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)