You can get all the available PowerUps using the coins you obtain when placing the different words on the game grid.
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.