Board Thread:Skin Requests/@comment-26879691-20160415200616/@comment-31507215-20180924205625

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 * 1) Click on the picture of the skin.
 * 2) Click the "More Info" button on the top-right of the window that pops up.
 * 3) Click the picture of the skin on that page.
 * 4) Right-click on the image and select "Save Image As".

That should give you the image, which you should be able to set as your skin, either in the launcher or at minecraft.net.