ok, to add more detail, vechiclewiringproducts sell all you need

a junction box to extend the live from the engine bay to the boot

1metre of black 300amp cable, to have some earth the engine to the chassis in the engine bay and some from the battery to the chassis in the boot

around 7-8 metres of red to run to the rear, via a FIA kill switch

get proper clamp ends, again see my sig build for pictures of the parts

get a dry cell battery for safety