Can i use the airport express going to royal garden hotel?

The airport express cannot take you to your hotel directly. If you choose to take the airport express, you need to stop at Kowloon Station and then take a taxi to reach your hotel. The Kowloon station is about 2 kilometers away from your hotel.
You can take the bus A21 to reach Mody Road, Chatham Road South. Then getting off the bus, you can ask the local people to find the exact position of your hotel and walk there. The bus stop is around 300 meters.
The bus is much cheaper than taking airport express.