There are many different methods for carrying and loading kayaks. One way to carry your kayak is by placing the upper cockpit edge on your shoulder. Another method is to lift it canoe style, holding it by the thigh braces. To load the boat onto your car by yourself, stand behind the car and rest the bow of the kayak on your rear car rack bar or roof. Move to the back/stern of the kayak (hold onto it!), then lift the stern and slide the entire kayak forward onto the rack.
This same method can work from the side of your car. Rest one end of the kayak on your car, then lift the other end. If you are concerned about scratching your car or kayak, place a towel on the roof or rack for protection. (Minor scratches do not harm the kayak.) Tie your boat securely to the roof rack. Run bow and stern lines directly to your car, with only minimal tension. (These lines are just insurance, in case the lines holding your boat to the rack loosen.) Too much tension on the bow and stern lines can distort the shape of your boat. Your local paddlesports shop can help you find a kayak rack that fits your car and budget.