It is a Torah comandment to hang mezuzot on our doorposts. Mezuzot, in turn, remind of G-d's presence and of our duty to fulfill G-d's commandments. Mezuzot are affixed to the doorposts of each room of the house and business, except the bathroom. The Mezuzot is placed on the right doorpost, as one enters the room, shoulder height. They should be placed in a slightly slanted position so that the top points toward the inside of the room.
The phonetic blessing is:
Barukh ata Adonai Eloheinu Melekj ha-olam, asher kidshanu b'mitzvatov v'tzivanu likbo-a mezuzah
blessed are you, Adonai ou G-d, ruler of the universe, Who sanctifies us with holy commandments and commands us to fix a mezuzah