At this point you will place the kayak on the roof rack. These steps assume you are only transporting one boat on the roof of your car at a time. There is an old joke in the whitewater boating world that says you shouldn't put a boat on the roof rack facing backwards. They say if you do you'll end up going down the river facing the wrong way. The truth is that some boats, especially whitewater kayaks, fit better with the stern facing the front of the car.
If you are tieing the kayak straight to the crossbars of the roof rack, as these pictures show, then you'll be placing the boat up-side down on the rack. If you are using kayak carrier pads or special attachments on the roof rack you can place the kayak right-side up. You'll have to use trial and error to decide which way the boat is better off, facing front or rear.
If you are placing a whitewater kayak the roof rack, try it first backwards and push the cockpit combing up against the inside of the back cross bar. The air pressure from the wind against the kayak will keep the kayak pushed up against the rear crossbar this way. If you are placing a sea or recreational kayak, make sure nothing is hanging off the deck that will dent and damage the roof of the car. When placing a canoe on a roof rack it should be centered on the crossbars of the rack.