Ah ok, making more sense! So using one that is there already...I'd use the lead that you linked to and insert that into the 'bottom slot' of, say number 10, which I tested already, and then just fire a fuse in to the slot to bridge from existing wire and my new red wire with that connection from eBay.?
What size fuse? 5 amp?
As an aside, could I use power going to the aircon? And tap in to its power source?