I see the rail pass does not go the Vernazza. Where does the rail pass stop and then how do you get to Vernazza?
Use www.trenitalia.com
choose English as the language.
Then go from Venezia Santa Lucia to Vernazza.
Choose a date in the next 7 days as regional trains don't show beyond that date.
Choose 00 as the time, so you will see all options since morning.
There are several solutions available. Via Florence-Pisa-La Spezia, via Milan-Genoa, via Bologna-Parma-La Spezia.
Choose the one that is best for your schedule.