Ok, so you still have to have the job with Nook. You know that part when he gives you paper to write on to deliver to a villager Well, exit the building after he gives you paper for that, then enter the building again. When he asks if you need more paper, click "Grand Idea!." Exit the building after he gives you more paper, then repeat the whole "exit building, enter building, talk to Nook, Grand Idea" process.