1 Airport express to Kowloon station. It may be closed depending on disruptions.
2 taxi
3 Cityflyer service A21. Need to walk or transfer to get to terminal. There's a bus terminal nearby, Google for bus services.
Take A21, alight at or near Humphreys Ave.
Cross Nathan road, walk along Hai Phong Road, then turn right into Canton Road to get to the China Ferry Terminal. A bit of a walk but cant help it.
Hai Phong Rd is quite wide .. still ok to push luggage.
The "ferry terminal" ie Harbour City near the TST Bus Terminal infront of Star Ferry is actually for cruise ships. The fast ferry to Macau is further away from this bus terminal.
EDIT: just found that from HK friend, instead of walking, can transfer to Bus 281A along Nathan Road ... this bus goes right in front of the China Ferry terminal building.
If take Airport Express to Kowloon Station, then take KMB 281A to alight along Canton Road (1 stop), just before the ferry terminal building ... this could be faster.