Googlemaps may be suitable for you particularly if you can view on large screen.
If you wish to begin at "the starting marker", from estacion de autobuses in Ferrol make your way to Rua Real and walk the entire length of this towards the marina. You will, eventually, pass the Parador hotel on your left. From here you are now walking the Camino in reverse to the marina, but it will be easier to ask for directions to waterfront / marina.
At this time of year the small tourist office booth opposite starting point will be closed. The main tourist office is in town ( perhaps way back near start of Rua Real ). You could get your first sello in the Parador.
I think the bus makes a stop in town before the bus station so perhaps you could ask driver or passengers if this stop would be suitable.
Buen Camino.