I'll just try to answer this in the simplest way I can think of.
To make your own banner and icon just use editing programs such as Photoshop, PhotoScape or Gimp or any other that could help but you probably already knew this.
To upload a new icon and banner for the spot, just go to the spot you made and follow the instructions that link gives you. I hope this helps! :D
I also hope I explained how to do this well, just please let me know if I didn't.
