Most of us had to figure it out. The rest of this is done by memory so take it with a big "maybe." The velcro straps go at the top between the metal and plastic. There is a loop at the bottom that goes around the floor board support.
What MIC_Rulz said although I have found that you can actually take the Velcro strap at the top over the top of the bar as well. Makes it easier than trying to thread between metal and plastic. Don't tighten up the Velcro until the end or you'll never get it on. They barely give you enough length on the straps.