Sample Data isn’t automatically added to your site, for most people this wouldn’t be beneficial and you should only import WordPress sample data on a fresh/empty installation. That said, if you want to import the sample data and make your site look just like the live demo it’s very easy to do so! Simply activate the recommended One Click Demo Importer plugin and click the import button:
Once you are done you can and should delete the One Click Demo Import plugin as you will no longer needed. However, if it looks like not all your content was uploaded (this is due to server restrictions) you can try clicking the button a second time to try and download any missing content.
Important – Regenerate Image Sizes:
To speed up demo imports and to give you time to select your custom image sizes only the main images are loaded to your site and not all the cropped images. So you will want to setup your image cropping options and regenerate your thumbnails once the import is complete. Please see the documentation here.