Simply click anywhere outside of the document elements using the selection tool.
Or you can:
- Go to Edit > Deselect All
On the right side of your InDesign screen, you should see the "Document" pane. From here you can:
- Change the document preset by using the drop-down arrow
- Change the page orientation by choosing portrait or landscape
- Manually adjust the page size
- Adjust your margins (if you're using them)
Check out our guide to change how InDesign displays your page measurements.