Hi,
What do you want to do? If you want to start out with files you find on the internet, what do you want to do with them? (eg. print sheet music for the piano, but take out the piano part to play along with; start from scratch and enter some sheet music, etc.)
By knowing what you want to do, and how you want to accomplish it, we can give better answers about what to do to get there
ttfn,
Sherry