Just take the person to whom you want to sell your car & visit any traffic department(at Madina khalifa or Mattar Qadeem or Souq Waqif).Take documents with you(Cars,yours & 3rd party).Visit them & register the car on his/her name. And obviuosly you know what to do with money?means the price.Hope so you'll understand my answer.
Be happy & keep smiling