It depends on where you leave from Shatin. I suppose you leave from Shatin KCR Station, then take the Bus 89X to Kowloon Bay MTR Station. You then cross the bridge to Telford Plaza and there're free shuttle buses (near the bus station) which will take you to the EMAX area.
If you leave from other parts of Shatin, I think there are still many buses that can take you to Kowloon Bay MTR Station. Hope it helps!