This feature is for premium members only. It allows the team users to duplicate projects and share/edit with the rest of the team members.
Click on a project and select Duplicate URL.
A window will pop up with a link, click on Copy to duplicate the URL.
Now you can share the project with your team members in various way. All you have to do is paste the link and send to them.
They can click on the link, copy and paste the it in a new window. It will have a pop up window asking you to Create New project. After you change the name, click Continue.
The project you shared with your team members will appear in their account as a duplicated version.