I am in version 2.79 and I can't figure out how to get in the "select faces" mode so I can do the insets.
The face select mode can be found at the bottom of the 3D viewport in Blender 2.79. See the image below :)
In 2.79, if you want to use a shortcut key, CTRL + TAB while in Edit mode will provide a popup menu from which you can choose Vertices, Edges, or Faces.