How do you spec in wow

Down at the bottom of the screen, next to your spells button, after you get to level 10, is a talents button. Here you have 3 different pages on a dialog box. Depending on your class these will all be named differently. On Priests it's Discipline, Holy, Shadow, on Warlocks it's Affliction, Demonology, Destruction, on Mages it's Arcane, Frost and Fire ....
you only get points at level 10 and up, 1 per level. A spec generally has skills and talents that complement each other, to make higher damage output or stun ability or healing output.