There are thousands of Mancala variations, but winning Mancala in a single turn is impossible in most game versions. The best first move is going to be the third hole, which places the last pebble in the Mancala zone. This scores a point and gives the player a second move.
Players can follow up that first move with the hole that drops a pebble in the opponent's third hole to keep them from repeating the same opening move. Try to keep the hole next to the Mancala zone empty because anytime a player drops a stone in there, his or her next turn automatically scores a point and gives them an extra turn.