First of all,download some skin from http://css.gamebanana.com/skins. When you are ready extract the files and go to your Counter Strike Source folder.Then open strike>custom and make folder with the name my_custom_stuff.Once you do this copy skin files and paste them in my_custom_stuff.( Important!Copy only materials,models,scripts and sound.Good luck non-steam players.I hope i helped you!You can also see:http://css.gamebanana.com/tuts/53