Choose a notation program with which to compose. There are plenty of options, including Finale, Sibelius, Notation Composer, and MuseScore (free). While the price of the programs varies, most work in a similar fashion. All the programs allow you to play back your composition to hear what you've written.
Open your notation software and start a new blank score. Type the title of your song, composer name, and copyright notice in the initial dialogue box. This information will appear on your new score.
Define the instrument parts you will include in your sheet music. You can choose from guitars, bass, vocals, piano, woodwinds, brass, and even add drum parts. Selecting instruments will alter your sheet music to accommodate the parts. Set a key signature and time signature for your song.
Add notes to your sheet music by selecting the note value from the toolbar or "Notes" menu. Move your cursor over the music staff and click the location on the staff where you want to place the note. Place notes, rests, and other music symbols on the staff to create your bars of music. The note values will automatically adjust as you add notes and other symbols, ensuring each bar of music maintains the proper number of beats.
Add lyrics to your song. Choose the "Lyrics" option. This allows you to type words beneath the music staff. The placement of lyrics is free form, so you can place the words you write under the note that applies to each word.
Save your song, then use the playback option on the toolbar to play your song back to you. To make changes to any notes that don't sound right, click on the note or section of notes you want to delete and add new notes by selecting the proper note value and clicking on the staff to place them. When you're finished editing, print your sheet music on regular printing paper. The music staff and symbols print along with your song.