The bus runs on a schedule irrespective. It is every hour or two. Ideally, confirm with them especially for arrival, but we also simply turned up to ride the bus to the hotel from the station. It was not full. Worst case, there are taxis that will cost equivalent of S$20-25 to the hotel.
The shuttle is located to the right of the exit when you leave the station. It is on the side with all the city buses, taxis and other shuttles. Pretty easy to find.