Select the Pages... menu item from the Site menu (example.com in the example below, though yours may have a different name) in the toolbar.
This reveals the The side-frame for page administration.
Hit Add page.
You’re now asked for some basic settings for the new page.
Just give it a Title - call it “Home”. You can ignore the rest for now.
You will notice that the slug is completed automatically, based on the Title.
When you are finished entering these fields, press Save. The page editing form is replaced with the page list. It’s a short list: you only have one item in it.
In the meantime to see the page you’ve just created, press Home in the page list; it’ll be displayed in the main frame: