Login to GAFX website. Producer can be contacted in either of the below ways.
1.If the Producer has already contacted the Artist on the same Project
Select INBOX option from Top right corner of the Profile page. In the PRIVATE MESSAGE page, you can see there exists a separate message window for Project and Producer combination. This can be used to communicate with Producer of your project.
2. Go to the Project 'workspace' where you are currently working on the given Project. Use the Private message box for contacting the Producer.