If you created your project through the template selector (as opposed to clicking the single Chart or Map button in your Library), you can have multiple pages in your project.
To add a page, deselect any charts or objects in your project or click outside the project canvas. Then click the Add page button in the right sidebar. There you will be able to select a blank canvas or one of the predefined pages.
Delete a page by either using the backspace button on your keyboard or by clicking the trash icon next to the page.
To reuse a page, make a copy with the Duplicate button.
Change the order by dragging and dropping them up and down the list.
To learn how to add page transitions, head over to the article about Adding and editing page transitions.