One of the two blue wires will connect to Ground and the other will be wired to the 86 terminal of the cooling fan relay along with the wire from the engine temp sensor. One of these two switches will close, completing the trigger circuit, closing the relay and send power to the electric fan. A third switch could be installed if you wanted to control the fan manually but is not required.

The two black wires are the Binary or compressor safety switch circuit and will be spliced into the compressor wire.