How do I change my desktop wallpaper on a mac without losing the picture?

On my computer, I scanned a picture of myself and put it as my desktop wallpaper. Then I deleted the scan, and now I can no longer find the picture I scanned. I want to change my background because I am older now, but I still like the picture. How do I keep it by putting it in iphoto or something? if i right click the desktop it says it will let me change the picture, but it does not show the other oneHow do I change my desktop wallpaper on a mac without losing the picture?
in the top L of the sreen -click the apple

go down to system prefrences

click desktop or screensaver

click and drag the pic 2 ur desktop

and then change the pic

i cant find my scan

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