This tutorial will help you to install custom skins to Portal 2, just follow these steps: 1.Download any skin. 2.Export "pak01_dir.vpk" to desktop. 3.Go to the Portal 2 root folder and create folder "portal2_dlc3". 4.Put your "pak01_dir" into "portal2_dlc3". 5.Wait for the game to finish loading,if it doesn't start close it with Task Manager and open it again. 6.Enjoy your skin.