Trailerable boat cover

I got one from wmart. It has 2 bungee cords and a rope that wraps around the boat twice. The instructions wernt very clear. My understanding was you run the rope through the loops and cross under the hull. doesn't say where to start and what to do with the excess rope. I suppose its open to interpretation. Any suggestions?
FIN

I have one if it's on fiberglass-- if it's not a custom cover I wouldn't pull my boat with it on. The wind will get under it and it'll beat the crap out of the gel-coat. jmho :eek: