Where are stops of free shuttle bus from HK Airport. I will stay in Island Pacific Hotel.

I known that the free Airport Express Shuttle Bus Service is not from the Airport. I wonder where I catch the free shuttle bus ? I arrive on Sunday at terminal 1 and I stay in Island Pacific Hotel. So, where I need to get off from Airport Express train to catch my bus? At HK central station or kawloon? Bus H1? Do I have to show the driver my airport Express train and airline tickets?