[noun (receiver)] + は + [noun (giver)] + に / から + [noun] + を + もらう
もらう means "to get", "to receive". The one who receives is the subject, the one who gives takes に or から, and the thing takes を. The polite form is もらいます.
When the receiver is you, わたくし私は is usually left out.
Either marks a person who gives. A company, a school or any organisation takes から.
When someone gives something to you, you can tell it from either side. With もらう you are the subject; with くれる the giver is the subject and takes が.
The giver of もらう is never you. When you give something to someone, the verb is あげる.
These go beyond receiving a thing from an equal.
From a teacher, a boss or a customer, polite speech uses the humble いただく in place of もらう.
After a て-form, もらう means having something done for you. That is its own grammar point, てもらう.