Paladins put Librams in the Relic slot. (Druids > Idols, Shammies > Totems, Death Knights > Sigils)
The first libram you likely find will be a quest reward in Hellfire Peninsula in the early 60s. There is 1 BoE libram in the game that you can use in the 50s, but it's pretty useless. Don't worry about them in the early game at all.