trouble with fuse

hi guys, this is my problem. I want a led to turn on when I turn the outside lights on, I asked for help here and someone suggested for me to tap into the brown wire in the kick panel, I have a 98 navigator. I stripped the cable and wrapped an inline fuse holder and then wrapped another cable from the holder to the led in the back, then grounded the led, then put a 15amp fuse in the fuse holder. problem is this, whenever I turn the outside lights on, it blows the fuse from the truck, not from the fuse holder. what should I do? can I put in a bigger fuse in the truck? what is my problem? if anybody can help me out here, ill appriciate it, thanksjdawg