It is implied that the king had Joab brought before him so that he could speak to him. The full meaning of this can be made clear. Alternate translation: "Then the king summoned Joab and said to him" (See: [[rc://en/ta/man/jit/figs-explicit]])
The phrase "See now" indicates that what follows is a polite request for the hearer to pay attention. "Please listen carefully: I" See how you translated similar words in [2 Samuel 13:24](../13/24.md).
This refers to what Joab wants the king to do. The full meaning of this statement can be made clear. Alternate translation: "what you want me to do" (See: [[rc://en/ta/man/jit/figs-explicit]])