This is the website ~ http://www.noteflight.com
This is the help-site ~ http://www.noteflight.com/info/help
This is where I post my answered questions ~ click HERE.
It is FREE. You don't have to download anything because this is an Online Version. You just have to open and account with them.
'Noteflight' is an online music writing application that lets you create, view, print and hear music notation with professional quality, right in your web browser. Work on a score from any computer on the Internet, share with other users.
Sign up for a free account (Up to 10 scores per account), or purchase a Noteflight Crescendo (unlimited Scores).
After you've created your score you can save it as a PDF, JPG, PNG and/or Midi file.
I just found it recently and am still new to it.