OP asked a simple question, how to get there :).

Anyways, coming from airport road (C ring or new arrival terminal), keeping going straight on the corniche. Pass by 2 parking exits on the right and take the third right. You will arrive at the parking. Park your car, buy tickets worth 2QAR from the white kiosk. Stand in queue and wait for the bus to take you to the ship. This right turn is just before the new museum (blue color)