Final answer:
Pharaoh learns about Joseph's dream interpreting ability from his cupbearer, who experienced Joseph's accurate interpretations while imprisoned with him.
Step-by-step explanation:
In the biblical account, it is Pharaoh's cupbearer who tells Pharaoh about Joseph's ability to interpret dreams. The cupbearer had been imprisoned with Joseph and experienced Joseph's accurate dream interpretation firsthand. After Pharaoh has his own troubling dreams that none of his magicians or wise men could interpret, the cupbearer then recalls Joseph's skill and mentions him to Pharaoh, which leads to Joseph being summoned and interpreting Pharaoh's dreams.