Pretty self explanatory and should come naturally, but if you need help here's a quick guide.
1. Start the game
2. Find some words
3. Rotate the board
4. Find more words
Achievement should pop mid game.
Edit: If you're not able to unlock this, keep in mind this is in beta and only open to US accounts. If your Live account is in another country you will likely not be able to unlock these achievements at this time.