Speak to the Priest of Mara in Riften. You can also buy a Amulet of Mara from him.
I married Farkcus from The Companions. Marriage in this game is pretty poor compared to marriage in Fable.
Farkas, his name is Farkas! You don't remember the name of your character's husband?

I dunno, I think marriage in this game looks to be much better than Fable. Then again, I don't like Fable.
Anyway, I thought I was going for Farkas too, but I'm also liking Derkeethus. And there's that orc companion with the hard to remember name. And Argis, too. I yet have to decide who would suit better my heroine's personality.