This is done in Goat Z-before outbreak. Simply jump down from the spawn in the coffin and go down hill where the crashed UFO and barn are located. On the far side of the barn is a small goat pen with an opening. Upon entering, time seems to slow down and you can act like a goat. You will know you are in the right location because Goat Simulator will pop up on the screen as an objective. There is also a collectible goat in the small shed by the hay if you want it.
Simply stay inside the gated pen for 5 minutes and the achievement is yours.