How do I book a shuttle bus service from my Hotel to Airport on the day of my departure

Hello, I wanted to use the shuttle bus service to go to and from my Hotel when I visit Hong Kong. I have read the details about arranging transport to the Hotel from the international terminal. But I cannot find out how to use your service from my Hotel to the airport on my day of departure. Do I book a service through the service desk at the Hotel? I hope you can help. Many thanks