You will find the corresponding option at:
Dashboard >> Appearance >> Customize >> General >> Layouts
You will find the following options:
Pre Content Loader – You have the option to enable or disable the same, it will allow you to show loader before loading content.
Site Layout – Allows you to select full-width or Boxed-layout.
Sticky Sidebar – Allows you to enable or disable the sticky sidebar.
Site Container Width – Allows you to set the width of the container that holds the site area ( px or % ). Default is 1170px.