Summarize:

Bingo scorecards have 25 randomly numbered squares on them, with the word "BINGO" written across the top. Your goal is to cover 5 of those squares in a vertical, horizontal, or diagonal row.  You can find Bingo scorecards online at your local hobby store. If you're playing Bingo with kids, you can print blank Bingo scorecards from off the internet and write in your own words, symbols, or pictures in the squares. In standard Bingo, there are 75 different letter-number combinations. Each letter-number combination corresponds with a square on the scorecards.   For example, all of the numbers in the "B" column on the scorecard correspond with "B" letter-number combinations. If the caller chooses "B-9," you would look for the "9" square under the "B" column. If you're looking for a simpler version of Bingo to play with kids, you can use pictures or words instead of letter-number combinations. In Bingo, the caller is the person that reads out the letters and numbers that determine which squares get covered on everyone's scorecards. The caller still gets to play the game with everyone else. If you're playing at a Bingo hall, there will already be a designated caller. In that case, the caller will not be playing with everyone else. Each player needs at least 1 scorecard. Players can use more than 1 scorecard, as long as they can keep track of all the letters and numbers on the different cards.  Playing with multiple scorecards increases your chances of winning, but it's trickier since you have more squares to keep track of. When you're playing with multiple scorecards, it's possible to win on more than one scorecard in the same game. In Bingo, the square in the center of everyone's scorecard is considered a free space. Everyone starts out with 1 chip over that space. These letters and numbers can be written down on small pieces of paper and then folded up, or you can use actual Bingo balls that have letters and numbers on them. They just need to correspond with the letters and numbers on the scorecards.  Put the pieces of paper or Bingo balls in a bucket, bowl, or Bingo spinner so the caller can choose them at random. If you're playing Bingo with kids and the scorecards have pictures or words on them, give the caller corresponding pictures or words to choose from.
Get at least 1 scorecard for each player. Explain to everyone how the game's letter-number combinations work. Choose a player to be the caller. Pass out scorecards to all the players. Place a chip on the square in the center of your scorecard. Give the caller the letters and numbers they'll call out in the game.