Just do every mission that you get, and by the time you reach chapter 6, you'll get a mission that gives you an emote that looks like scissors. Once you have that one, you should have all of the dancing emotes. Now just click through your emotes til you get it!
As a note (thanks to risseless), some people have reported losing all of their emotes, so you might want to use your emote as soon as you get it, so that if you lose them you still have the progress toward the achievement.