How did agustus become emporor?

Answer 1

Emperor is a modern word. He became First Citizen after defeating Mark Antony in the Civil War. He progressively took on background powers to control the aristocracy trying to assume powers which had fed the civil war. He assumed the powers of a tribune of the plebs in Rome; pro-consul outside the city; and control of the border provinces which had the legions. The rest he left with the Senate.

He would not have accepted any title associated with kingship as that is what brought the knives out against his adoptive father Julius Caesar.

Answer 2

he was the foster son to the dictator Julius Caesar