Import demo issues

I have an existing site published and hosted by Host Gator. After downloading, installing and activating the Highend theme, I would like to install one of the demos and begin customizing in WordPress before publishing the new site.

When I try to customize the demo within WordPress, all I see in the editor is my existing site which uses another theme, not the Highend demo content I tried to import.

So it seems something went wrong with the demo import or I need to do something different to activate the demo within wordpress and begin editing?