Headunit problems

Hi, got a 2000 Corsa Sport 1.4 16v just taken out my original headunit, and ive replaced it with a Alpine CDA-9812RB,its a 60x4 watt headunit and since its so prowerfull i have to directly fit it to the battery which i have done!! All wires are connected and and i am getting power from the battery as the grounding sparks if i tap it agaisnt the metal!! the problem is that the headunit wont switch on!! In the manual it says i have to connect a wire up to the fusebox aswell!! didnt now this?? is it true?? and if so how to do it?? the wire that should be connected to the fusebox just has a femal bullet on it!! any help much apreciated!! Cheers