i used to fit and remove these at work, honda company cars all have one. verry easy to fit,
first work out were you what to hide the box( in my disco 1 its glued to the inside of the flap by the drivers knees).
then find a earth for the black wire,
ignition switched wire for the red one easest found at the back of the sterio, ( may be need to solder the blue wire to the red depending on the age of the unit)
the yellow wire goes to the back of the stereo on the mute wire.
then work out were you what the speaker, mine is by the diff lock leave (d1) but honda are buy the drivers feat cable tided to a loom.
mount the mike and button ( mine mike is on the drivers grab handle , button between dial pop and door.)
then assuming you have already ran the wires from were you put the box, plug them all in. they all are different plugs so you cant get it wrong.
then the button should light up when the ignition is on, then pair the phone i think the pass code is 0000.
hope that helps, and makes some scene maybe ?