How can I see a Cube ?

Hey guys , I’m Thai and poor in English . I wish you could understand what I’ll said.

Well, I just start learning Unity and I’ve got some ploblem.
(I took some tutorial from Youtube)
At first I try to importing a Cube but in the scene I only can see a line of the cube
and I can’t see the symbol of MainCamera
(but in the tutorial it is a grey cube and have a picture of camera)

What should I do ? somebody please help me.

‘Thanks you’

( this picture is from tutotrial )

( and this is from my project )

what do you mean “has its normals outside”