Hi, and welcome to the forum
Some owners have tried hooking into the fuse box leading to problems due to the cars computer.
The best way with modern cars, is to use your own wiring (not the cars loom), and use the car battery as the 12V source.
Here is a diagram to hook up extra lights based on 2 x 70W. Use 4mm for the lights wiring and 1.5mm for the control relay wiring.
You need a power relay as shown and wire it through a new cabin switch and connect to existing lights depending on how you want them to operate. (The cabin switch shown is non- illuminating, but you can buy an illuminating one if you want, by hooking its internal light from the switch wire feed, through its light and then down to earth, so it lights when the new lights go on).
I have shown the way to get the new lights working only when the dipped lights are om, though you could instead connect that wire to the side lights instead, so your new lights will operate after side lights are on. This control switching prevents your new lights staying on after you leave the car, no matter the cabin switch position.
You will have to go through the front bulkhead with the 1.5mm control wiring using either existing holes or new one drilled, fix rubber grommit in bulkhead and seal with silicon sealer to prevent any rain water ingress.
I would also add a small in-line fuse of 5A for protection of the 1.5mm control wiring at where you are hooking up to the existing lights, its not really needed but is extra protection, that i usually put in (not shown in diagram).
Any more questions, ask away. Cheers Colin.