Son getting ball python. Cage setup help please

[Kaorte]

So your saying tape it to UTH outside of the glass.. like on the very bottom. Where the top is stuck to the glass?

I don't really understand what you are confused about. You just tape it right on the UTH outside the enclosure. The UTH has a top and a bottom. The top is stuck on the glass, and the bottom is open to the air.