Could I use the free service if my hotel is Royal Park Hotel in hong kong? How do I get into my hotel with it?

Yes, you can on condition that you should take Airport Express first! Upon getting off at Kowloon station, take shuttle bus line K4 to get off at East Tsim Sha Tsui. Then walk to Lippo Sun Plaza to catch the free bus of your hotel to reach there!

There is another way without using the free buses. Airport bus no. A41 can directly take you to this hotel in 35-40min.