Stacking floor of 16 Manufacturers follow the signs if you are building it with the top drone floor (https://satisfactory-calculator.com/en/blueprints/index/details/id/10566/name/16+Manufacturer+Top+Floor+with+Drones) otherwise you can feed it from the lower levels but connect opposite of the signs tell you to move input higher and output on the bottom level.

Remember to mirror each floor as you stack them. All inputs and outputs snap easily to the next floor with a single elevator.

Remember to go from output to input with the elevators so they snap

There are 3 different output lanes you need to connect to the other floor and the 4 input ones which is really easy as the elevators will snap in place.