looking for a good place to put it. should I use sharpie?

I had some clear stickers made with the whole registration number card that I got. It has the faa logo and so forth. I put it on the underside of my drone

You don't have to mark your bird up with  Sharpie.  FAA says a sticker is fine. I used a Sharpie inside battery compartment to mark distinctive markings in case it gets lost, so no one can claim its theirs if they find it.  Assuming of course you find them with your bird.