Hiya Sally,
I've recently invested in the whole set-up (still sitting in a box til I get time to install it
) You'll need-
Energiser (main/battery or you can get dual powered ones too)
Earth system (metal poles driven into the ground)
Lead out cable (if you're using a mains system)
Insulators (you can buy ones that screw onto existing posts or use the plastic posts with a metal spike on)
Tape/wire/cord - I like the tape for visability.
Notices to hang on your fence to alert anyone who may come into contact with it.
and you might want to consider a lightening diverter kit (in the case of mains set-ups)
I think that's about everything
Fearing do a good manual that explains everything - you can order it (for free) from their website. I bought most of my stuff from them and Paddock perfection & would recommend both for good service.
HTH
Karen x