It's just a case of using the existing wires on the ignition, there should be one from position 3, so this needs to go one side of the switch and a feed taken from the ignition pos 2 live to the other, this is replicating the setup of the current switch.

All it will do is send power to a relay which then switches the main feed to the starter, that is what draws a lot of current, but yes in any case you do need to make sure your switch is rated correctly etc.

Martin