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Click the Windows logo in the bottom-left corner of the screen. Type paint 3d into Start, then click the Paint 3D option at the top of the Start window. It's in the middle of the Paint 3D window. This option is near the middle of the window. Doing so opens a new window. Go to the location of the photo for which you want to replace the background, then click the photo once to select it. It's in the bottom-right corner of the window. Your image will be opened in Paint 3D. This three-by-three grid icon is in the upper-right side of the Paint 3D window. Doing so opens a new column on the right side of the window. It's in the right-hand column. The switch will turn blue {"smallUrl":"https:\/\/www.wikihow.com\/images\/0\/0a\/Windows10switchon.png","bigUrl":"\/images\/thumb\/0\/0a\/Windows10switchon.png\/57px-Windows10switchon.png","smallWidth":460,"smallHeight":218,"bigWidth":"57","bigHeight":"27","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"http:\/\/en.wikipedia.org\/wiki\/Public_domain\">Public Domain<\/a><br>\n<\/p><\/div>"}. You'll find this tab near the left-hand side of the Paint 3D window. This will ensure that your final image requires as little editing as possible. Try to get the edges as close to the part of the image that you want to keep as possible without being inside of it. It's on the right side of the page. Anything that is both outlined in blue and fully colored (e.g., not greyed out) will be saved when you crop the photo. If parts of the section you want to save aren't included, or if parts that you don't want to save are included, you can add or remove sections by doing the following:   Add — Click the Add icon at the top of the right-hand column, then draw an outline around the section of the image that you want to include.  Remove — Click the Remove icon at the top of the right-hand column, then draw an outline around the section of the image that you want to remove. It's on the right side of the page. Press Ctrl+X to do so. You should see the selected portion of your image disappear from the Paint 3D window. It's a folder-shaped icon in the top-left corner of the window. Do the following:  Click Open. Click Browse files. Click Don't save when prompted. Select the image you want to use as a background. Click Open. Once the background image opens, press Ctrl+V to paste the copied section of your original image onto the background. If necessary, you can resize the original image by clicking and dragging one of its corners inward or outward. To save your project as one image, do the following:  Click the folder-shaped Menu icon in the top-left corner of the window. Click Save as. Click Image. Enter a name for your image, then click a save location (e.g., Desktop). Click Save.

Summary:
Open Start . Open Paint 3D. Click Open. Click Browse files. Select a photo. Click Open. Click the Canvas tab. Click the grey "Transparent canvas" switch . Click Magic Select. Drag the edges of the canvas in to surround your subject. Click Next. Add or remove any sections you want to keep or delete. Click Done. Copy the selection to your clipboard. Click Menu. Open your background image. Add the original image to the background. Save your image.