This is located within the wrestle-cowboy yeti guardian area of the Hub. Go left past the yeti and down the slope. There will be a small square area with two dark circles and metal pipes. This is the shower. To get the achievement simply interact with the pipes by using your
attack, water will come out and the achievement should pop soon after. You might have to hit
a few times or jump and hit it for the water to come out. Either side of the shower works just look to see that the shower 'knob' spins when you do your attack.