Hey Buddy, It is quite easy and doesn't drain my battery at all. This is going to be brief, ill take some pictures afterwards so it makes more sense.
Simple buy some LED Strips off eBay or where ever locally. I believe I bought 3 meters and had extra to cut off. It has a adhesive backing to stick on the tray sides (clean the tray sides before sticking them on)
Basically this
LED Strip - Ebay
I got some twin core wire from work and fed it through the baby seat latch hole (removed the baby seat latch)
Wired it into my Sub power and ground which is located on the amp behind my passanger seat (was too lazy to wire it to the battery etc) wired a light up switch using basic electronic knowledge [nothing special lol]
Hid all the wires in conduct and tucked it, You cant see it once the seat is back to rest. It was honestly a lazy set up but it works a treat. Lights up my whole front yard/street.