Once that was decided the project got really easy :) I centered the fabric over the headboard and laid it down on the floor. Then I used an electric stapler to tack it down - just stretched the fabric over each side, wrapping it like a present. You have to press kind of hard for the electric stapler to get the staple all the way through the decor fabric and padding and into the wood inside.
I'm not ready to show you the whole room yet but here's the finished headboard...waiting for a bed!