Here "you" is singular and refers to the barren woman. She represents herself and all of her descendants. Alternate translation: "For you and your descendants will spread out" (See: [[rc://en/ta/man/translate/figs-you]] and [[rc://en/ta/man/translate/figs-synecdoche]])
Here "nations" represents the people. Alternate translation: "will conquer the people of other nations" (See: [[rc://en/ta/man/translate/figs-metonymy]])