Can anyone tell me how to hook up a battery isolator??

I just bought an opt. red and a yellow top battery...got a PAC 200 isolator to put between them....anyone know how to hook up the isolator...i run batt. in parallel i know(pos. pos, neg neg....but was just unsure about the isolator....any help would be appreciated...Thanks...oh yeah..(The isolator has 2 big term, and 2 small ones..any ref. to which wires go on what))

two big posts + one in from alternator and out to second battery and the small ones one negative and the other is the ignition switch I cant remember which is which