How do you save your farm in FarmVille on facebook?

At this time limited expansion is available to all users. All players will start the game with a 12x12 farm and can currently expand their farms up to a 20x20 plantation by either meeting game requirements and purchasing the land with coins, or through paying for it outright using FarmCash.

Each time that a farm expands 2 additional plots will appear on both of the bottom borders of the farm. It's not possible to skip ahead in farm sizes, so if you'd like the 16x16 farm you'll be required to purchase the 14x14 farm first.

You have to buy more space. Go to the market tab and then to the Expand farm button and purchase the size of farm that you want and can afford.

You expand your farm in Farmville by adding friends.