newbie in need of assistance

I'm just learning cad (autocad and Vectorworks)

If I make a rectangle (or any other 2D shape) and extrude it, what
would be the easiest way to close up one end? For example, turn an
extrude square into a solid box.

Also, how to I apply a material or image to a single surface? I have
situations where I need to apply a custom material/image to a specific
segment of a 3d shape.

Thanks for any/all help!!!

 

If you extrude a rectangle (a closed polyline) in Autocad, you end up
with a solid box - although you may have to 'hide' to appreciate that.
To print the box out as a solid object you will also need to hide the
'hidden' lines. The manual explains how to do all of this, but if
you're really struggling let us know.

The answer to the second question is there are a couple of ways. I
suspect that the most appropriate one to use depends on the complexity
of the material, and of the object to which it is applied, and also
how the areas to which the material ISN'T applied should appear.