Mad Cows Weapons 3.0 Problems

Yeah i downloaded Mad Cows Weapons 3.0 Beta and i tried putting it in addons,and my main gmod directory but it doesnt show up in game.but i think i installed it correctly because after i make a singleplayer game i get a error in console about Madcows Sniper.Can anyone help me install madcows weapons the right way?thank you