Demo pages with blog and portfolio grids are not included in the demo content package, as otherwise demo import file would be too large and would fail on some servers.
Instead, you are able to easily add blog and portfolio grids from Scape Templates library.
To display blog, you first need to create a content block with a post grid in it, and then assign that content block to be used on your blog page in Theme Options. More information can be found in theme documentation.