I am no expert but I would suggest you start with a melody or chord prgression.

Then figure out a song title. That tells you what the song is about.

Now write out what you you want to say about the title. It may be a story or a description of feelings and emotions the title triggers. There is no need to make it rhyme.

Now you can begin to tell the story in lines that rhyme.

Writing songs is not easy but I hope that my ideas may help to get you started.

With a bit of luck someone might reply who has better knowledge.

All the best,

Joe.