How do I go to Hong Kong Island (specfically to Island Pacific Hotel) from Airport?

Actually, bus will be more conveient. Shuttle bus no. A10 can take you to Connaught Garden, Connaught Road West, from which you can walk to your hotel.

If by rail, you need to take Airport Express Train to Kowloon Station and transfer to bus no. 970 or 972 to Connaught Garden, Connaught Road West. Then walk there.