Save that design.Then go to the giant sewing machine near sable.Talk to her and say you want to use it.Then it will give you options.Click the make QR code.Then select your Hatsune Miku design.Then there will be 4 screenshots.When you're done,save your game.(You wiill find those screenshots of the QR codes in your 3DS pictures.Take out the SD card on the side and if you have a SD card reader(if you have a laptop,there should be one) put in the SD card.Save the pictures to your computer off the screenshots,and upload it to the Able Sisters designs.