Two conditions need to be met in order to use a power-up.
1) You need to have power-ups in your inventory. These are signified by the green circle with the white exclamation mark at the top of the screen (between the keys and the orange tickets). Power-ups can be earned by leveling up, completing BINGOs, opening luggage, or by purchasing them with the in-game currency coins.
2) There is a green power bar (like a thermometer) that rises with time during your match. This rises faster by jumps when you daub squares on each of your cards. Once the meter is full, a power-up is randomly selected from your inventory and is displayed at the top of the meter. It flashes to indicate that it is ready to be used. Note that the meter tends to rise faster when playing multiple cards, because for every card that has the same daubed number, the meter makes another jump.
Once a power-up is used, it is removed from your inventory. The meter is reset and you must wait for it to fill again before you can use another power-up, provided you still have more in your inventory. You can earn this Achievement without spending any real currency, it just takes time. Once you have played 50 power-ups across all your matches, the Achievement will pop.