i want to travel on the left of the train so i can see the views over the sea. What seat numbers should i choose when booking on line?
Can't help you with Frecciabianca trains from Pisa to Genoa.
However both the Intercity trains from Pisa to Genova Piazza Principe and Thello trains from there to Nice Ville normally travel on these parts of their journeys with first class at the front of the train (first is coaches 1 and 2 on Intercity, 11 and 12 on Thello). So you would need to choose window seats at the bottom of the seat diagrams.
Note that this is not guaranteed, as trains can be reversed in service.
Note also that there is nothing to stop you sitting in any empty seat that you wish to, as long as you move if someone boards the train at a later station with a reservation for that seat.