To Set Up Full-width / Boxed layout, follow steps below:
Step1 :
Open Customizer: Dashboard->Apperance->Customize
Step 2:
Open “Layout” tab, then open “Layout General ” tab.
Step 3:
In Layout General section, choose Layout style from drop-down menu.
FULL-WIDTH LAYOUT
BOXED LAYOUT
Step 4:
Clikck on “Save & Publish button to save changes.