Hi, need some help wiring in the standard amplifier please.

I have upgraded my HU-603 to a HU-803 with parts sourced from breakers yard. I have changed the head unit with no problems, all illumination works etc which i was worried about. I have fitted the centre speaker but dont know if it works yet coz....

The amp wiring has been chopped off from the fusebox and i'm not sure how to wire it back in. All i have is a power lead running from the amp and need to know how to wire it back to the fusebox please.

Any help much appreciated.

Shaun