Connect all cathodes together into 2 wires. Then have 2 wires from battery. One on positive, one on neutral. Positive wire put an inline fuse box in (5amp fuse should be ok I think), then wire straight to the positive wire for the cathodes. On the neutral / earth wire, put in a switch. can be a push switch or the most common being the rocker switch. Then from the other terminal on the switch, connect it to the wire on the neutral battery wire.