When I look at any number of pages in Rally or many of the apps such as Custom List 2.0, the Group By, Show Fields and Export buttons are grayed out and cannot be used.
This happens when there are no work items of your chosen type in the project.
As soon as someone creates work items of the chosen type, the buttons will become active.
So if you've selected User Story as the Work Item Type, then once someone creates a story in that project, the buttons will become active.