after finishing the mission institutionalized and not joining the institution is there a way back to the institution. i want to go back and kill everyone

If you saw a mission called "Banished From the Institute" come up then the option to go back is gone to for you. If not, just fast travel there on the pip boy and you'll appear at the bottom of the elevator. But if you start killing people you won't be able to fast travel out and you'll have to make it up to the relay up top.

ok thanks

which location on the map do i fast travel to