The picture is of the sinner offering the "parts of his body" to his master or king. One's "body parts" are a synecdoche for the whole person. Alternate translation: "Do not offer yourselves to sin so that you do what is not right" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Here "now living" refers to the believer's new spiritual life. Alternate translation: "But offer yourselves to God, because he has given you new spiritual life" or "But offer yourselves to God, as those who had died and are now alive" (See: [[rc://en/ta/man/translate/figs-explicit]])
Here "parts of your body" is a synecdoche that refers to the whole person. Alternate translation: "let God use you for what is pleasing to him" (See: [[rc://en/ta/man/translate/figs-synecdoche]])