go to riften, speak with a priest in the temple of mara about marriage, then u need the amulet of mara either buy it from him or random drop, use the amulet and if the person u want to marry is able to do so u will get another dialogue something like "u like me right" then she ask u and u answer me too something like that, then u go again to the temple of mara make an appoinment

u have 24 hrs to get married thats about it
about the mate asking about benefits, yes aside from rp or w/e, ur wife/husband will make u food once a day to help with stats reg if im correct and also will put up a shop so she/he will be able to give u gold daily
cheerz hope this helpz