When viewing the "select world" map with your gummi ship, press Square to access the "Gummi Garage". From here it asks you if you want to view the tutorial on ship-building, - which is highly advised. After viewing the tutorial, select "Garage". Select your ship and add a useful gummi block to it. Press Circle to back out after you're done adding blocks to your ship and press "save". The trophy should be yours.