Final answer:
The first step in the witches' prophecy concerning Macbeth's rise to power is him becoming Thane of Cawdor. This prophecy sets in motion the events that lead to his rise and subsequent fall.
Step-by-step explanation:
In Shakespeare's play Macbeth, the witches' prophecy concerning Macbeth's rise to power begins with him Becoming Thane of Cawdor. This is the first step predicted by the witches when they meet Macbeth and Banquo in the forest (Act 1, Scene 3). The witches present three prophecies, with the first being that Macbeth will become Thane of Cawdor. The prophecy is soon confirmed when Ross and Angus arrive to inform Macbeth that the king has bestowed the title of Thane of Cawdor upon him, setting in motion the other prophecies concerning his rise and subsequent fall.
Learn more about Witches' prophecy in Macbeth