Like a text processor helps getting your text on printed paper, so does a music processor help you getting your notes on paper.
You probably already know (more or less) how to write music using pen and paper (if you don't, the accompaniment features offered by MusiCAD will serve as an aid in developing music writing skills).
If you have managed to arrive at this page you have at least some basic knowledge about using a computer.
That's all you need!
You may save yourself some time if you start with the tutorial