To ennoble someone is to make them a Lord or a Baroness — to bestow a noble title upon them. The Queen of England has the power to ennoble people, turning Paul McCartney into Sir Paul McCartney, for example.
One way to use the verb ennoble is to mean, literally, "make someone a noble or a member of the nobility." It can also mean "bestow or lend dignity to" or "make dignified." You could say, "Reading great books ennobles the mind," or "Treating others with kindness ennobles a person." Ennoble comes from the Old French ennoblir, from the prefix en-, "put in," and the Latin root nobilis, "excellent, superior, or splendid."