The way i did it was “all at once”
The rear attachment is the key to everything. You must pull the top as tight as possible around the rear bar. Once that is done, the rest can be played with to get it all tight. Use clamps on the front to test how it will pull when closed. With the front clamped, but not glued, you will be able to see how the sides will pull tight at the door window.
It is harder to explain than to do. If you got your seat covers on, it should be a breeze. Not nearly as hard on the fingers.