When in Goat MMO, you can hit
for a map of the area. You have to enter areas to "discover" them in MMO fashion, so use the map inside the spoiler for reference if you have not previously visited the mentioned locations in the following guide:
This achievement is gained in Bullgrurzh at the south-center of the map. The only way into this area is through Glarblargle Beach to the west. You'll find a bunch of little wooden shacks with a big upward ramp leading into Bullgrurzh.
Once you arrive, there is a passage to your right heading downward that you want to take until you come across a big, floating, golden wheel. Headbutt it to get your achievement.