Before uploading the demo you need to know that WordPress creates a sample page and a sample post when it is installed. You can delete them. Please take a look at Appearance > Widgets. WordPress also sets some default widgets in the widget area. Delete them also if you want.
If you would like to get demo content pages as on the demo website, please follow the instructions:
- Navigate to Tools > Import.
- Click on WordPress Importer and install the plugin. After the installation, click Activate plugin & Run importer.
- Click Browse and upload the file with dummy data from the \dummy-data\ folder in the theme package you've downloaded from ThemeForest.
- Check Download and import file attachments to import media files, and click Submit.