I walked the freedom trail. Pretty cool. You can get maps at the Boston Commons. If you are in no hurry, buy a tour bus pass. It’s like $20 and you can use it for 24 hours. Then you can do sightseeing as you go place to place.
Go see Old Ironside, too, the oldest commissioned ship in the Navy. Check out the poop deck. 
Cheers kinda sucks cause only the steps look the same as the show. At the bottom of the steps is a hostess station.