You can get all the available PowerUps using the coins you obtain by winning games and participating in game modes such as "Guess the Word" and "Word Search".
To get them, go to the Shop, which can be found on the lower right corner of the screen.
Once you enter, you'll see your coin balance on the upper left corner, followed by the corresponding balance of each of the PowerUps. These are: Top Play, X-Ray Glasses, Word Spotter and Magic Play.
If you scroll down, you will see the different packs you can get for each one of them, with their corresponding prices, in packs of 1, 3 or 5 PowerUps.
Now you can also buy PowerUps during games! To display the Shop, you must press the PowerUp you want to buy, which you will see above the game board.
Once you do, you will see the different options to compare PowerUps, and you can use them in the game you are playing.