After loading the game, you need to select the Bet amount and then place it by tapping on the "Place Bet" icon.
Figure 1: How to place a bet
The basic rule of Blackjack is to beat the dealer's hand without going over 21 points. If your total points exceed 21, you will be busted regardless of the dealer's hand. If both you and the dealer's points become the same, it is a "Push", meaning no one wins, and both you and the dealer get the bet amount back.
Figure 2: Result "Bust"
Figure 3: Result "Push"