I have one too, and wiring it in is simple. It sits in-line with the stock wiring, and you simply have to mate the plugs on the HRC box to those on the stock loom.

I removed the HRC plugs on the input side, crimped new pins on and inserted them into the stock loom, then filled the voids between them with silicone sealant (it's a standard aircraft 'battle damage repair' technique and works perfectly well).

The output plug connects into the PGM unit as per the normal loom.
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