I'm recommending Sworkit to everyone I know, in fact. Because for just under $1, you get an amazing fitness resource right on your iPhone or Android.
Feel free to give the free lite version a try, but really, I'd pay the buck and get the full suite of features the app has to offer, like customized workouts and tracking based on your fitness goals and desires; videos of each move so you know what you're doing (and don't hurt yourself); as well as the ability to challenge friends.
You simply choose from Strength Training or Yoga, Cardio, and More, then decide what you're looking for, whether it's 10 minutes focused on just your butt, or "Anything Goes" cardio for 45 minutes. You can even create a completely custom workout too. Then click start, and a lovely woman with a British accent tells you what to do first (or hit mute if you prefer to figure it out on your own).
And if you still have no idea how the move works, just click on the video for more explanation. That's it! Bathing suit season, here I come. -Kristen