How do I go from hkia to tst by air express,please help,thanks.

Hi, you can take Airport Express Train to Tsing Yi Station, where you can transfer to subway Tung Chung Line to Nam Cheong Station. At this station, you can take West Rail Line to East TST and then walk to your destination.

Or you can take bus S1 to reach Tung Chung where you can find mtr Tung Chung Station to take Tung Chung Line to reach Lai King. At this station, you can find Tsuen Wan Line to reach TST directly.
You can also take airport shutlle bus No. A21 can take you from HKIA to TST directly within an hour.