No need to loosen the cables at the bars. Just undo the mount screws at the carb ends.
Seat the carbs. Be sure they are pushed on all the way.
Wrap the pull cable in its groove under the bell and secure its end in the slot.
Seat the pull cable into its holder and secure the screws.
Put the ball end of the push cable into its groove on the top of the bell, then push the end of its cable into its holder, and secure the screws.