To Create a new project, go to the projects list panel and click on the "Create New Project" button.
In the popup that appears, you can enter the name of the project and choose which account you want it under. Any other users with access to the account will also get access to this new project.
If you do not yet have any account or would like to create a new account, you can click on the 'Create Account' tab, then enter the name of the account and click 'Create'. This will then return to the 'Choose Account' panel with your new account selected.
Finally click 'Start Project' to create the project. This will take you to the project panel where you can start creating your 3D scenes.