How do you jump on the red pipe in Mario and Luigi Bowsers inside story?

First make sure that Bowser has the "Ground Pound" ability. Around the 1st Map nearest to the Link between Bumpsy Plains and Bubble Lake, bring Bowser up to the slope at the left side of the map, and then ground pound. Bowser should land in a secret place with beans and blocks etc, and there will be a yellow pipe.