Make sure that any songs you would like to submit on the Marketplace are first uploaded to the Library. (Click here to learn how to upload your songs to the Library.)
You can submit your songs on the Library by clicking "View", and "Submit to Marketplace"
By submitting your songs, your songs are on the marketplace where buyers can see. They can check and hold your song for further negotiation. (These songs are not visible to the other creator users.)
When you submit your song to the Marketplace, you can also submit it to any Briefs you like.