Procure a sample of the air from your fruit's container using the syringe that comes with the chromatography kit. Depending on the size and scope of the sample in question, this could involve opening the sealed crate of fruit and using the plunger to trap an air sample, or sliding the needle into a plastic container and withdrawing air.
Inject the gas sample into the chromatograph's glass or metal tube. For an ethylene test, the gas inside the tube will be nitrogen, and this "carrier gas" will push the tested air through the system. Activated aluminum is also in the tube to facilitate the separation of the sample into its component gases.
Turn on the chromatograph. A hydrogen flame will consume the samples, leaving behind electrons and ions. The chromatograph will then give you a readout of ethylene gas in parts per million (ppm).
Obtain the reading in parts per million and multiply that figure by the difference between the volume of the fruit's container and the fruit itself. Then, divide that figure by the weight of the fruit in grams and then by the number of hours it was encased in that container. You'll get an answer in nanoliters per gram per hour, which indicates how quickly ethylene is being produced.