Boston is easy to get around in with the T. Driving? Unless your a local, not so much.
The T gets you close to both locations.For Sterling Plaza (by Rowes Wharf) use Redline and get off at South Station then walk up the greenway north a few blocks. Or use the Orange/ Blueline and get off at State Street and walk south a few blocks.
For Dewey square get to the Redline and get off at South station. Walk upstairs.