Backgrounds help

I'd like the background image I see e.g. when I view my inbox and the image displayed for my stadium to be different but can't seem to find a way to do so. I'm using the Wannachup skin and have the Google Earth megapack and the FM 2018 Stadium Images megapack both downloaded and want to use the picture from the Google Earth megapack as my background and the FM18 Stadium Images one as my stadium picture. Thanks in advance
Please? It's my birthday. Well, it was.

Hope someone would help with this. Was wondering about the same thing as well.

By the way, newbie here. Whenever I'm taking a break from this particular interest, I'm usually found at home, feeding my Pomeranian with some treats and watching TV with my wife. And when we're not indoors, we would play catch in our backyard with our dog (though we had to secure one of those petsafe Stay+Play wireless dog fence, just so he wouldn’t stray far from our yard. Our neighbor had a weak wooden partition, and we once had an argument when the poor fella ended up on his lawn). Such a simple, yet, happy life. Cheers!