The script to The Miser never actually describes the setting of this play. All it tells us is that it is set in the city of Paris. And judging by the play's action, everything happens in the house of the miser Harpagon.
He is a wealthy man who clearly doesn't want people to know he has money (even to the extent of keeping his servants in rags), so you can imagine that his house is furnished with some old furniture that he refuses to replace or repair. Just imagine the house of a crazy, cheap old man, then set it back in 17th-century France, and you're good to go.
Thematically, it's important that the entire play takes place in Harpagon's house because the majority of the action in the play (and certainly all the problems and conflicts) is brought about by Harpagon's power and ability to control. Until the very end, Harpagon is the puppet master, pulling the strings and making the other characters dance. It's very much his house. And Harpagon is a dude who adopts the 'my house, my rules' mantra.
Luckily for everyone involved, the last scene shows the four lovers merrily exiting Harpagon's house, showing that they are no longer under his control. Freeeeeedom!