it should have the layout printed on the cover for some of the fuse boxes, however you can't always count on that (or the book) being the right way round or accurate, so you may have to do a lil guess work.
you can maybe save yourself a lil time by getting someone to buzz the rear wiper whilst you run a circuit tester / multimeter across the plug on the motor to see if any voltage at all to it. I would suspect not. If not then you know its fuse or broken wire, likely fuse.
Picture the scenario, heavy snow we've had over the winter, person gets in car, its cold and horrible, no one wants to get out to clear the rear window - i'll just use the wiper, oops the wipers just twitched and stopped, snow must be too heavy for it - presto popped a fuse.
I confess I know little about the brera - of the 5 Alfa's I've owned not 1 had a rear wiper, but fuse is where I'd be looking!