Before you can actually get married, you'll need to go to the Temple of Mara in Riften and learn about marriage in Skyrim by talking to
Maramal. He can be found in the Temple of Mara, and on occasion be found in "The Bee and the Barb" also in Riften.
After asking about the temple and learning about marriage, you will be able to buy a necklace for 200 gold that shows you're 'available'.
Buy and wear the necklace, and find yourself a partner. Your own race and gender does not impact the choices you can make.
A full list with name, race, gender, occupation and required quest/action can be found here:
http://elderscrolls.wikia.com/wiki/MarriageAfter choosing your partner, head back to the temple and arrange your wedding with Maramal. Wait for a day, but
NOT inside the temple, and re-enter to attend your marriage.
The achievement will unlock after saying 'I do'.