Can I harvest honey from a birdhouse that bees have made into a beehive?

Q. Help, I have a big about 12 by 12 bird house, bees have made there
hive in it and it's full, how do I get the honey? and save the bees
and
me."

A. Harvesting from the birdhouse would be very tricky.
I have a birdhouse about the same dimentions as the one you described
that someone brought to me and it is amazing how well it pollenates my
garden.

I would let your bees do their thing. You might also be able to catch a
swarm from the bird box in the spring.
I have captured 3 swarms from my bird box hive.
I then install them into a proper hive and they go like gang busters.

You seem to be interested in bees and honey,....... I would get yourself a
hive!