Stuck in non-default cube mode

For some reason I cannot get back to the default cube locale.

I was doing dusk blue tutorial and could not find the sub-surf menu. Finally did, but now cannot get back to default cube. Must have done something incorrect before that as things that are suppose to be tenacles are only troughs and sub-surf did not engage correctly. Ctrl x and/or x will erase screen, but upon clicking new same screen and project appears. I am new to this blender stuff, but before this was having little problem. I cannot find other ways to delete to return to new project!??

Go to menu File>Load Factory Settings then Ctrl-U to save as default settings OR just delete B.blend file.