How to go to repulse bay arcade from fo tan station just using train, no bus in HK?

It is impossible to only use trains to Repulse Bay Arcade from the Fo Tan Station.
You need to reach Central Station to take the bus line 6 or 6X to the Repulse Bay. From Fo Tan Station, you can take the East Rail Line to Kowloon Tung Station and then change to Kwun Tong Line to Prince Edward Station. Then change to line Tsuen Wan Line to Central Station. Then walk to the Exchange Square area to take the bus for Repulse Bay.