the "preparing the execution" render, was not part of BTT, Nightmare rendered it just to get people excited, just like my baby tori ashes jar I rendered.
as for DoF,
1. add a camera
2. click on the camera
3. in the attributes box, click the "depth" tab
4. check front and rear blur
5. under render settings add Depth of Field to the effects list
6. modify
7. click on the box with a plus in it next to the camera on the objects list
8. Ctrl+r or Shift+r
9. I'm not a walking tutorial, google could've taught you this, it taught me afterall