Press the item labelled 'Projects' on the left side of the dashboard.  If you don't yet have any projects, the screen will show a prominent green button to add your first.
To create a new project, press the 'New Project' button, and you'll be shown some Project Templates to choose from.  Templates include individual stories that make up the Project as well as the structure of the Project as a whole: reflecting an organisational relationship between the stories, their overall theme and the navigation your readers will use to traverse the Project.  A "Blank Project" template is available if you'd prefer to start without any sample content or structure.
A new project started from the blank template won’t have any stories in it yet, and it will have the name “Untitled project” which you can change to suit your project (e.g. “Winter 2022 Edition” or “Acme Website”).
You can go back to the main dashboard at any time by clicking the round "S" icon in the top left of the window.
On your dashboard, your new project will appear in the 'Projects' tab as a card with the name of your project and small thumbnails of any stories you added to it. Clicking on this card will take you back into the Project editor.
Please note: If you’re a current Hubs user, your existing Hubs will be automatically migrated to Projects. You’ll see these in your dashboard as Projects the next time you log in.