Hello y'all

I have a can of this air-con treatment bought from Ebay but no instructions came with it. Anyone know how to use it? Ofcourse i have emailed the seller but no reply as yet so figured someone here might know.

im pretty sure all i have to do is put it down in the passenger side, press it on and wait 15minutes for the gas to spread. However im unsure if the aircon has to be on along with the car's ignition. Any ideas?