Importing the demo content is part of the setup wizard but it can also be done using the One Click Demo Import plugin, by navigation to Appearance > One Click Demo Import.
The importer will help you start with the pre-built layouts from the demo and dummy content such as product pages, blog posts and widgets.
Cannot find the Import Demo Data section?
Sounds like the One Click Demo Import plugin is not installed/activated. Navigate to Appearance > Install Plugins to Install and activate it.