An idea only exists in your head or your journal. It does not exist in any other concrete form we can manipulate into something that makes the "something better." We need to think about - "form."
The "Form" is what the idea looks like when realized in our world. I wanted to communicate my insights and learnings to the world. I chose the "written word" as a "form" to express my ideas.
You may have an idea for a piece that speaks to people's attraction to poor relationships. You want to express this idea in the form of a song with lyrics. Or perhaps through an instrumental piece? Maybe it's visual and not aural?
You express your idea to the world through "form."
You'll know the form you need by thinking about a few points.
Identify the talents you can bring to bear.
Think about how people will want to interact with your idea.
Meditate and use your "mind's eye" to visualize.
Create better art by starting first with an idea, then think about how you'll express it to the world. Identify the form.