It can be put on the inside... that's where mine is. If you have a sunroof, I dont think it will really fit on the roof, and plus, I think the antennas look dumb. As far as how to put it inside, all I did was cut a small hole in the rear deck/hatch cover thing so the antenna leads can go through, but under where you want to put the antenna so you dont see the cables. As far as making the antenna stick to the rear deck, I put a piece of ABS plastic, or something you can screw down to the cover. Clean the surface you just put down with the alcohol wipe provided, then let that evaporate (dry), then press the antenna on it. Now, run the cables along the bottom of the cover out of the way, to your tuner box.
I'm not at my house right now, but I can take a picture of my antenna when I get home tonight, or when I get up in the morning. Let me know if you have any more questions.

"Anyone who has never made a mistake has never tried anything new."
-Albert Einstein