Hi Fred,
look here on this map:
http://www.vtp.it/pages/navi/mappaCrociere.jsp
You will find the Piazzale Roma on the right hand. To reach the terminal, you have to go first in direction northwest (you can see the road on the map), than left in direction south west. The way is not comfortable. You better take a cab. We did so too. It is not expensive. About € 5.
Regards
Uwe