Before uploading the demo you need to know that wordpress create a sample page and a sample post when installing wordpress. You can delete them. Please take a look to the Widgets. Wordpress also set some default widgets in the widget area. Delete them also if wanted.
You can import the demo settings with just one click. Go to Appearance > Theme Options > Import / Export.
Choose a import options and click on the image to import. The importing action can take some seconds. That's it.
If you want to get demo content pages like on demo website need install plugin WordPress Importer.
Visit Tools -> Import in the WordPress dashboard, select dummy_data.xml from Demo Content folder in zip archive.