Page layout free – remove all default template

Hello

I am trying with no success at all to use a page without sidebar, and no orientation I´ve read here seems to work so far.

I even tryed tocustomize root css styles, but the effect either don´t apply or take more than one day to show…

Will this work?
http://www.wpbeginner.com/wp-themes/how-to-create-a-custom-page-in-wordpress/
Am I going still to be able to use Visual composer?

Please help!