How do you tell? I think it's quite interesting that there's little way to tell, for a layman, what or where any of these go. It's not like it says "guest room" or "kitchen" like the panel at your house.
Tour the ballistic missile submarine Le Redoutable, the largest submarine you can tour without security clearance, and one of the only ballistic missile subs fully accessible to the general public. - Page 1
Creepy corridor - On the right are all the computers charged with programming the missiles with directions on how to get to their targets. Along the left are all the missiles. They're blocked off now so you can't walk in and around them.
Where's Scotty? Those huge tubes carry the high-pressure steam from the reactor to the turbines. These are heavily insulated, as you'd guess. On the right is one of two electrical generators (the other was removed during the museum conversion).