If you want your child to use it, you need to register/sign-up your child using a user email address and password. When signed-up, the default setting is composing piano music with two lines of music. But, he/she can remove the bottom staff(line of music) by clicking on the bottom line, then going to the "Staff" tab and selecting "Remove Staff". He/she can compose on that staff. If he/she wants to change the instrument name from piano to their own instrument, go to the "Staff" tab again and select "Change Instrument".