Instructions
Interact with the Sims. Once you found a Sim who gets along with your Sim, keep interacting. This means calling the Sim, inviting him over and helping him when he needs help.
Flirt with the other Sim, or perform the actions available that will let them know that you want to pursue a romantic relationship with them. You open up more options as you interact with a Sim. Start with asking about the Sim's day, then compliment his outfit, then start to hug or kiss the Sim if the option becomes available.
Propose marriage to the Sim when the action becomes available. Only propose if your relationship meter is higher than 80 percent and the Sim is happy. It is possible for the Sim to reject the proposal if they do not feel the same way, are hungry, tired or have to use the bathroom. If rejected, continue to work on the relationship and propose again. Also, note that since you want to move into the Sim's home, propose while in his home, not yours.
Get married to the Sim. Once the Sim has accepted your proposal, both of you will immediately change into wedding attire and get married. You are also given the option to move in. If you are in his house, then you move into this house together.
Move in. Once you have agreed to move into your new spouse's home, your assets add to your partner's items, and any previous children move in as well.