Instructions
Open your Web browser and use a search engine to locate a website with free "Minecraft" skins. Search for terms like "Minecraft skin" or "Minecraft character skin," or visit the "Community" page of the official "Minecraft" website for links to several popular player-created skinning sites.
Choose a skin you like and click on its link to begin your download. Select a location on your hard drive to save the file and wait for the download to complete.
Go to the official "Minecraft" website and log in with your username and password. Click on the "Preferences" link at the top of the page. Click the "Browse" button under the "Replace this Skin" heading and browse to the location on your hard drive containing your downloaded skin.
Click the "Upload Image" button to install the skin. When the installation is complete, your new skin will appear in the character portrait under "Your Current Skin" in the Preferences menu.
Launch your "Minecraft" client and enter the game to see your new character skin in action.