How do you ask a girl to marry you in sims 3

you can marry a sim by becoming friends with the girl/boy you want you sim to
marry. Ask if the girl or boy is single. It might say yes. If they do, do anything . It"s a seven-year Sunday night staple that I"ve dedicated over 4,200 minutes, or 70 hours, or yup that"s right, nearly 3 days...
How do you ask a girl to marry you in sims 3