Kitchen Sink Spray Gun Inquiry
If the faucet set currently installed in the sink is sprayer compatible, it should have a third tube coming out of the faucet body/mixing valve. Also note, unless there is a sprayer shut off valve or a fitting that automatically stops any flow to the sprayer when the mating plug is not connected, it would shoot a hard stream of water out anytime the water was turned on. My guess is that there is no sprayer feed in the set you have installed now.  If you put a pic of the bottom of the set from under the sink, we would know for sure.