How do I get to catch the sightseeing bus from the port and how far is it in Shanghai

Hi, but which port do you mean? Then I can give you the detailed information.
Anyway, the sightseeing buses have two lines: line 1 and line 2. The buses pass and stop at many stations. About the specific stops, you can search on the website:
https://www.travelchinaguide.com/cityguides/shanghai/transportation/sightseeing-bus.htm#voice