I have installed a Alpine radion in my 2011 Fiat Ducato 2,3 motorhome, and i have installed a Alpine reverse camera aswell.
But now i have a trouble. In the install book it says this:

Fuse box, left black connector, pin 8, white/ red cable = reverse light.

I am not sure what connector they are talking about and i dont know how to re-wire this.

Anyone with any idea how to do it?

You'd have to unscrew the fuse box to get at the connector and they are probably intending you to use a spawn of satan scotchlok to wire it.

It would appear to be referencing the 32-way connector shown as "LL" in the attachment.

This is taken from the "1st Ducato Training Manual" which is available in the download section of the forum).