If it has a metal clip:
You know thats a good question. Ive seen them mount to the top of the lower section of the ecm cover, then the top piece of the ecm cover going over it.
I have also seen them mount to the cover that goes by your feet, to the left of the ecm cover.
If it has a plastic clip, ive seen them mount to the metal structure of the dash, like it clips into 2 holes, behind the big black plastic piece.
Hopefully i did not confuse you too much.
PS, there are also big black plastic pieces with holes cut in them for the light to shine thru.
I also upgrade the lights to larger bulbs to get the interior brighter.
HTH
BW