How do you win at Tic Tac Toe?

RULES FOR TIC-TAC-TOE.The game is played on a grid that's 3 squares by 3 squares.You are X, your friend (or the computer in this case) is O. … The first player to get 3 of her marks in a row (up, down, across, or diagonally) is the winner.When all 9 squares are full, the game is over.