Welcome, congrats on your soon-to-be-arriving new snake.
The tstat probe goes between the uth and the enclosure.
Just a few suggestions on the setup:
1) As said above, more clutter would be a good idea. A BP that feels safe and secure will be most likely to thrive, while a snake that feels scared or nervous will be more likely to refuse food.
2) It is often suggested to use 2 identical hides, one on either end. Snakes can be picky about which hide they use and will often sacrifice warmth or stay in a hide that is too warm because it's the only place they feel safe.
3) The rock hide is actually for fish and not the best choice, and the skull isn't a great hide either. Cool decoration, but not great for practicality.
4) The enclosure may be too big for a juvenile BP. Plenty of people have success with that size enclosure, but it can also be public enemy number one with new snakes.
Just food for thought, as there are more than one way to do things...
Good luck! Keep us posted and share some pics when your new snake arrives!!
Feel free to ask any more questions you may have.