One method of creating a song is to think of a catchy song title, then to ask some questions about what the title might mean, the play on words it expresses or what feelings it evokes. Then you can decide on a song structure.
A standard song structure is verse/chorus/verse/chorus/bridge/chorus, but this structure is by no means mandatory. Think about the questions regarding the title and begin to answer some of them in a structured form, perhaps using one answer for the chorus and one answer for each verse. Consider using imagery or emotion in the answers. Play around with the wording to produce a natural rhythmic lyric that facilitates melody in both the verses and chorus. Change the emotion or the emphasis until the verses and chorus make sense melodically and as a song story. Make a rough recording of what you have so far.
Start adding simple chord progressions while playing back the recording. Keep track of chords you like by taking notes or recording the progressions that fit the melody. A bridge is a climax in the song story and can bring the theme, the verses and chorus together. It is usually a different chord progression, so repeat the first few steps to create a bridge that fits the song. Once all of these elements are in place, make a simple recording of just the chords and a vocal and then expand it with other instruments, parts and harmonies.