If you'd like to change the installed demo on your website, you'll need to agree with resetting your WordPress. All settings, pages, posts, custom posts, categories, menus, etc. will be removed.
Navigate to Consulting > Demo Import and select the new demo from the list.
When you click on the Import Demo a popup window will appear with the message that you have to verify that you "Understand that there is NO UNDO" (mark the relative option) and click Reset Now.
After completing the reset you can proceed with the Demo Import tool and start to import the demo content.