If you are on the Cloud Starter plan, you will be limited to a single Project, and won't be able to create another until you upgrade to Cloud Pro.
A Project is a grouping of apps much like a folder. To share an app with a specific group of members of your Workspace, you can create a Project from the Home or Projects pages (if you have permission).
All Workspaces come with a default Project. All apps are shared with the
default group automatically.
When a new member is added to your Workspace, you can add them to specific Projects.
You can change which Project an app is part of on the App settings page.