How do I set backgrounds for two monitors?

[Geek-9pm]

I am using current version of Windows 10.
I have a dual monitor thing with my old Del 745 PC.
Works good for me. My one issue is the backgrounds.
Look here.

Google has some images for dual monitors, but I do not understand how to do the setup. Please point me in the right direction. Show how I got lost. 

[look]

I use Ultramon I have 2 different size monitors & use different backgrounds on each.