Choose a Bingo room from the Main Lobby and you will be brought to the Card Selection screen for that room. Choose the number of Bingo Cards you would like to play and how many Cherries you want to bet. Betting more Cherries increases the payouts, unlocks the ability to get 4 Bingos on one card (Mega Bingo) and increases the number of Puzzle Pieces that appear on each Card. After setting your bet, select the number of cards you want to play by tapping on the green button with the total Cherry cost.
 
Next you will have the opportunity to pay Coins for Powerups. You can pay for Standard Powerups like Bonus XP and Bonus Coin Tiles or you can pay more Coins for extra-special Powerups, like Instant Bingo and free Double Daub! Or if you do not wish to use Powerups, you can just tap the Play Bingo button and skip. Once you tap Play, the Cherries and Coins you paid for the round are deducted and you are taken to your Bingo round.

Good luck!
 
For more information on Powerups please see, "What are Powerups?"