There are 2 versions, one with magnets, one with straps. Obviously I got the one with straps.
Basically, that black panel that goes around your gas cap, the strap from the front of the bag loops around the very front of that black panel and the strap from the back of the bag hooks onto the very back of that panel. You have to take the seat off to get to the very back of that black panel.
It took a bit of fiddling, but was not bad, and has stayed secure.
Each of the straps has a quick disconnect, so when I fuel, I just disconnect the back strap, flip the bag up and fuel. It stands up out of the way on its own.
The bag does not have a lot of capacity, but great for extra glasses, gloves etc.... and has compartments with windows for a GPS and phone.
Does exactly what I wanted it to do.