No Add on button

i am trying tio get some addons to work but i dont have an addon button on my chracter screen. i have asked many people what tgo do and they ahve all tried to help but nothing i do works. CAn someone tell em why my addon button wont appear. I ahve windows vista and in the World of Warcraft folder, all there is is an Interface folder with an Addons fodler inside of it...please help