Speak to Maxan Anvol in Dun Morogh.
Hey! <name>! Got a minute?!
Ya been following the Light now for long enough that you find your way to Maxan Anvol in Kharanos. He'll teach ya more about the path yer following, and if you prove worthy, give ya yer first set of robes to denote your station as a priest.
Now get goin'! As soon as yer done here, head through the tunnel--he'll be waitin' for ya.
Oh, so Branstock sent ya, did he? Good, good! He's right, it is 'bout time you started taking a much larger step into the Light. It'll build character and make ya stronger... an' that's what you'll need more than anything: strength of body... strength of will.