This achievement requires that you have 10 friends or more visible in the Social screen (Tools>Social). There are actually two ways to unlock this achievement:
Have 10 friends or more on your Xbox Live list that have played Kingdoms & Lords at some point. All friends that have at least created a kingdom and saved it to the cloud will show up.
If you have no friends at all that have played the game, ALL of your friends will show up in Social screen, which will get registered for 10 or more if you have that many total friends on Xbox Live.
So there are two approaches to earn this achievement. You can either find and friend request ten others that have played the game, which is the recommended route, or (temporarily?) remove all your friends that have played the game so ALL of your friends will appear and unlock the achievement that way. However, it is best to have as many friends as possible that play the game so the first method is recommended. Thanks to Avenged Remains for providing clarification on this. This achievement will not pop until after the tutorial.