Open a Noteflight account. The account is free and requires no more information than your email address and the creation of a user name and password. Log into your account to begin writing your song.
Click "New Score." Choose private or shared, depending upon whether you want others to be able to view your music or not. A blank music sheet will appear. Click "Edit Title" at the top of the sheet and enter the title of your song. Click "Edit Composer" in the top right of the music sheet and enter the name of the composer.
Set the time signature and key signature of your song if necessary. The default is the key of C in a 4/4 time signature. To change the key and time signature, click on the time and key signature on the sheet and use the pop-up box to set new values.
Add the notes to your blank music sheet. Click anywhere on the sheet and select the note value you need from the palette. The palette contains a variety of notes, rests and other music symbols. Press any key on your keyboard to place the note, then click the note with your left mouse button and drag it to the position on the staff where you want to place it. Measures break apart automatically as you insert notes.
Add additional instruments to your music score by going to the "Score" menu and selecting "Add Part" above or below the current staff. To erase music you've written, click in front of the music notes and drag your mouse to select the note, then hit the delete key on your keyboard.
Enter lyrics to your song by going to the "Score" menu and clicking "Text," then choosing the "Lyrics" option. This allows you to type lyrics under the appropriate music staff and melody notes.
Play your finished composition back to make sure it sounds right. Go to the "Play" menu and select "Play From Start." If you're satisfied with your composition, click on the "Save" menu and save a copy of your song to your computer. You can choose to print or export your composition to a playable MIDI or WAV file from this menu as well.