Buy an Amulet of Mara from Maramal in Riften
Equip the Amulet of Mara
Speak to a marriageable NPC while wearing it
Complete the NPC’s required quest or favor quest if needed
Return to the NPC and choose the marriage dialogue
Go to the Temple of Mara in Riften
Speak to Maramal and arrange the wedding
Attend the wedding ceremony the next day
Choose your spouse after the ceremony
Move your spouse into your home if desired