“by your command.” More literally, “by your mouth,” with “mouth” being put by metonymy for what comes from it, the words and commands.
[See figure of speech “metonymy.”]
“be ruled.” The Hebrew text is literally, “kiss.” Thus, “by your mouth will all the people kiss.” The idiomatic use of “kiss” here most likely refers to being obedient and submitting to rule (cp. Ps. 2:12), but it could also refer more directly to paying homage to Joseph and then by extension obeying him. Thus the NASB translation: “and according to your command all my people shall do homage.”