Step 1: Testing the EL wire
Plug both orange EL wires into the splitter and the splitter into the inverter. Connect the screw terminal block with the power supply.
Plug the cord of the power supply into an outlet. If everything works, the EL wire lights up as shown in the picture and you hear a high pitched sound. This is normal and comes from the inverter.
(If it does not work make sure to unplug the power cord first before you manipulate anything else.)
Step 2: Putting the inverter into the junction box
Cut holes on both ends of the junction box.
Insert first the screw terminal and then the connector as shown.
Putting the inverter in the box reduces noise and keeps the screw terminal dry (just in case).