Styling a brown sofa is an easy part. You are free to play with throws and achieve the look that you want. Go for fun throw pillows or blankets that will add coziness. You can always go for neutral shades. A colorful Persian rug will be a nice addition and anchor your pretty sofa.
If your living room is bright, then you are free to go with colorful pillows. As the sofa itself is neutral, you can go with bright accent colors to make it pop.