Before affixing a mezuzah to a doorpost, the following blessing is recited:
Hebrew: ברוך אתה ה’ אלוקנו מלך העולם אשר קדשנו במצותיו וצונו לקבוע מזוזה
Transliteration: Barukh ata Adonai Eloheinu Melekh ha-olam, asher kidshanu b’mitzvotav v’tzivanu likbo-a mezuzah.
Translation: Blessed are You, Adonai our God, Ruler of the universe, Who sanctifies us with holy commandments and commands us to fix a mezuzah.
If you have a number of mezuzah’s to place, you recite the blessing once (usually on the front door) , keeping the rest of the mezuzot in the house in mind. After reciting the blessing, no words are spoken until all mezozot are hung throughout the house.