Start by selecting the "Manage pages" from the bottom of right panel and click "Add page". Then you need to set the page name and click "Create".
Pages can be managed from the same place. You can move a page by dragging and dropping it where you want. If you want to delete a page, click the three dots on the right side of the page and select "Delete page".
You can also change the page group landing page, by clicking the three dots and selecting "Set as landing page". The first page is always the landing page.