You can watch this tutorial video to know more: https://www.youtube.com/watch?v=j6nz0Qte6s4&list=PLZSqbv2i8LOBCosw-vNCjyhmJ5BmrmCqA&index=6​

Theme settings > Layout

1 - Site Width

1.1- Full Width

1.2 - Boxed

1.3 - Content Full Width

1.4 - Wide 1600px

2 - Site Background

Note: Only set the background color & image with "BOXED" layout

Result:

​

​

From The4

Hope you success!!