DIY Cabin Air Filter

[AngelMoo]

I've had a look around, read this whole thread and it seemed like the best place to ask (if not, correct direction pointing would be welcome!)

I've got a slightly smelly aircon and before I try installing a filter I wanted to spray some antibacterial stuff into the system (Toyota AU wanted $50 for this). It was an effort but I finally found the spray... now I don't know where to spray it. Can someone tell me exactly where the aircon intake is?

Edit: just tried to put some product (turns out it's a foam, not aerosol) in the fan part under the side passenger glove box... well you can't spray a foam upwards so I didn't get any in the aircon. So now we're all out of ideas.