When the fun game starts-up you will be on your horse, in a small arena, with a very large red & white ball directly in front of you. There are a total of six gates - each is about twice the width of the ball - that you must push the ball through in less than 65 seconds (1:05 on their clock) to earn the achievement. They are:
Gate 1 - Directly in front of you.
Gate 2 - Directly in front of you.
Both of these gates require you do nothing except go fast and straight. If the ball hits the fence, don't be concerned as it will bounce back.
Gate 3 - at the end of the arena, hard right. Just circle past the ball, move it away from the fence and through the gate.
Gate 4 - another right turn, only about forty-five degrees, again, circle to the left of the ball and it will be bumped into the gate.
Gate 5 - straight in front of Gate 4, in the middle of the arena, so if you had a clean Gate 4 shot it will be an easy one.
Gate 6 - hard left and in the furthest corner of the arena. You don't need to go through any particular side, both are okay. So if you go beyond it quickly into the fence and bounce it off there back through the "back" of the gate it still counts.
Guaranteed that after two tries - this achievement will be yours.