How do I change my desktop picture size, it looks huge.....?

My default picture on my computer...(desktop background picture), looks really huge and kind of blurry, how can i change the size to make it fit the screen better, please tell me where to go......and how to make it work. I hope my question is clear, if not please let me know, thatnks.!How do I change my desktop picture size, it looks huge.....?
right click the mouse button on the default screen(startup screen),

then , properties%26gt;settings%26gt;screen resolution. change it to 800*600

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