Answer:
To create the plot of the play.
Step-by-step explanation:
The original material that Shakespeare used was taken from the story "Un Capitano Moro" written by Cinthio almost 100 years earlier, which tells the story of a very eloquent and honorable black man who became a great general, but who was betrayed by a man who pretended to be your ally. Shakespeare used this as a basis for creating and writing the entire Othelo storyline.