How can I take a bus from Shanghai Railway station, North Square to Wusong Cruise Terminal?

There is no direct transport mode, so you need to make a transfer.
From the railway station, you can take the subway line 3 top Baoyang Road. And then walk north about 250 yards to Baoyang Road bus to take the bus Baoshan 9 to Baoyang Road Bus Station. Getting off the bus, you will see the cruise port. Or you can take a taxi the whole way, and it would cost you CNY80 around.