Tim - When you buy a launch permit, you get two stickers about the size of a PennDot inspection sticker. They're self adhesive. You have to buy new ones every year, but you can buy them two years in advance.
I just stuck one on each side of the frame on the riser where the oar locks mount. When I got checked by a WCO, he had no problem where they were mounted.
There's more stuff that you need though. You have to have an audible warning device (I use a whistle) and a light if you float after dark. And don't forget your PFD - I believe a Type III is required.
I have an electric motor, but never used it on my boat. The required registration sticker and numbers must be displayed on either side, just like a "regular" boat. I made a lexan plate for each side, to be zip tied to the frame, but never registered my boat.