Decide which genre you want to create music for. Have a mental outline of just how this track will ideally sound. Select "Add Audio Track". Most songs start off with a very general sound which depends on the genre. This is your foundation on which you build the rest of the song.
Decide which instruments will help complete your song. Feel free to experiment with different chords as well. Again, the instruments you introduce to the song should complement the genre.
Now, add vocals as necessary. This can be done manually with a microphone or by taking some vocals that have been previously saved onto your computer. After inputting the desired singing, the program's editor can polish it off. Remember, it's very rare for vocals to span the whole song so place them accordingly.
Now that you have introduced the basics for a song, it's time to begin the process of editing. Here is where you "trim the fat." Any unwanted sounds or beats are removed from the final product.