Instructions
Navigate to the webpage containing the link for the Minecraft texture pack you want to install. Several websites, including planetminecraft.com, minecraft-textures.net and minecraftwb.com, host texture packs for Minecraft. Click the link to download it. Save the zip file containing the texture pack to your Desktop or browser's download directory.
Launch Minecraft. Enter your username and password and click "Login."
Click the "Mods and Texture Packs" button on the main Minecraft menu. Click the "Open Texture Pack Folder" button. Minecraft opens the Texturepacks folder in a new Windows Explorer window.
Click the "Start" menu button, then click "Computer." Navigate to the location in which you saved the downloaded texture pack zip file. Drag and drop the zip file into the Texturepacks folder window.
Close both Windows Explorer windows. Click the texture pack in the Minecraft window that you want to use. Click "Done" to complete the installation of the Minecraft texture pack.