The kill key goes into the recharge port to disrupt the electrical connection and shut the saber "off".
The recharge port will need to go either where the dummy switch cover is currently, or if you don't have a second switch hole with a switch cover you will need to drill a 12mm hole into the hilt to mount the recharge port. You either glue it in, or you can use the lock nut to secure it (super secret ez-mode for that
here).
When upgrading from Warrior to Champion, you will also need to replace the current latching switch with a
momentary switch.
You can reuse the current LED, but will need to add a
micro deans connector to the LED wires to connect it to the PnP kit. That's the only bit you can reuse from your current setup when upgrading to a Champion PnP kit. Or you can just buy a new
PnP LED if you're not confident in your soldering skills.