To specify your significant other:

1. click your name to the right of the picture on your main page;
2. click "What is your relationship status?";
3. select "in a relationship" or "married" in the menu that opens;
4. select your significant other from your list of friends or enter a name by clicking "Indicate name".

Your connection will be established once your significant other confirms it. Note that only users aged 13 or older can be "in a relationship" with a friend and only users aged 14 or older can be "married."