Head to the Workshops Area to the left of your Home. Inside your will find a student that has built you an Instrument Workshop. Learn how to catch Spirits and get Coins to end this Event.
Upon Completion: Warning: this quest is missable in the cactus diaries! Return home, talk to Lil' Cactus, go downstairs (watch him write the Event on the leaf), and go back upstairs to save your game before continuing.