Wallpaper question

Hello everyone, if this is not the proper spot then please move this thread. Apologize in advance.

I have a 2010 MBA hooked up with a second monitor on my desk. I've seen people post pictures of one wallpaper being extended onto both. How do I go about doing this? Maybe something like the picture below.

GGJstudios said:

I haven't read it all, but this may help: Crop, Stretch & Set A Single Wallpaper Across Multiple Mac Displays

Click to expand...

Thank you.

That app works great.