how to go to buddha temple from airport, and come back to airport?

Do you mean the Ten Thousand Buddhas Temple? If yes, you may take the Bus n42 (up) and get off at the Sha Tin Central Bus Terminus. Then walk to the temple.
When you come back to the airport, you need to walk to the Sha Tin Central Bus Terminus first, then take the a41(down), and get off at the airport.