You should learn to play the piccolo or another type of flute when you have a good foundation of playing the flute. Some players learn the piccolo after only six months, others never learn it or wait years. I waited about two and a half years. If you still have a hard time getting a consistent sound on the flute, you don't want to add another instrument to the mix. Use this time to refine your flute playing, and you may be ready to try the piccolo or alto flute in the next year.