Now you have it all: you’re the king, the thane of Cawdor, and the thane of Glamis
In this scene, Macbeth and Banquo meet the three witches. The three witches tell Macbeth that it is his fate to be the thane of Cawdor. The witches also tell Macbeth that it is his fate to be the king. Macbeth's fate might be to become the thane of Cawdor and to become king but he still has free will and can choose what to do.
In this scene, Macbeth returns from just killing Duncan and returns to Lady Macbeth. Macbeth tells Lady Macbeth that he successfully killed Duncan. It might be Macbeth's fate to kill Duncan but Macbeth had the free will to not kill Duncan. Macbeth still chose to kill Duncan even though he had the free will to not do it.
In this scene, Macbeth is king now. Macbeth might have had the fate to become king but the choices he made to become king were all his own choices. Macbeth could have chosen to not do everything he did but he thought it was his fate to be king and he has free will and chose to do it himself.