i have blue flex LED under dash lights, the instructions are terrible, and i just bought all the parts off common sense, i want to run them from my battery. i have a fuse holder, 20 amp fuses, rocker switch, and shrink tubing. how do i do this so called "simple" installation !?

Positive goes to positive terminal on your battery, which would also run to your toggle switch. Negative can be grounded anywhere that good solid metal contact can be made. And make sure the light gets grounded and so does the toggle switch. No different than hooking up a set of fog lights that will run off of a toggle.

That sounds like a bad idea because they can kill the battery if he forgets to turn them off.

First, if they are "Flex" (Ford Flex) ambient lighting LEDs than your going to require the module that controls them, and you need to build your own medium-speed CAN system. This is pretty involved.

If "Flex" means something else and NOT Ford Flex, I'd have to see what the parts consist of. If it is a simple LED strip basically "ready for 12-15V" than you should connect the switch to something that is hot only when the key is on, so you don't leave them on and kill your batter. I would connect to the backside of a fused circuit as well so it is protected from the factory fuse. LEDs will also need ground (obviously) and have to be physically mounted. Make sure they are mounted on something that doesn't get too hot because heat kills LEDs. Make sure you have no opportunities for your circuit to short out.

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they are really bright, i mean i would have to be pretty stupid or pretty facked up to forget to turn those things off haha