1. Right-click on the desktop and select "Personalize".
2. In the Personalization window, click on the "Background" tab.
3. Under the "Background" tab, you can choose from a variety of background images or colors.
4. To use a custom image as your background, click on the "Browse" button and select the image you want to use.
5. Once you have selected an image, you can adjust the fit and position of the image by using the controls in the "Position" section.
6. Click on the "Apply" button to save your changes.
Additional tips:
* You can also change your background by using the Windows 10 Settings app. To do this, open the Settings app and go to "Personalization" > "Background".
* If you want to use a slideshow of images as your background, you can select the "Slideshow" option in the "Background" tab.
* You can also change the color of your background by clicking on the "Solid color" option in the "Background" tab.