I didn't take pics of the wiring, but I can tell you what to do. My dual tone setup was off my 2007 G6, same as found on many American cars. I had a green wire and a black wire, the Mirage horn is a self grounding one wire horn. My green is my power and black ground on the dual tone, so I spliced my green to the wire on the Mirage and ran my black from the horn to the mounting bolt. This way I knew I had a good ground, using the same ground as factory.
The key to projects like this is knowing which wire is your hot and which is ground, also don't overload your circuits; a horn for a horn is pretty safe.
My horn could have been mounted directly where the factory one was, however I could not get both hands down to hold the horn and thread the bolt in; it was too awkward so I relocated the horn towards the center as mentioned.
How it sounds after the switch (also my first YouTube video lol):
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View my fuel log 2014 Mirage DE 1.2 manual: 37.6 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.2 mpg (Imp)