XF 1.4 narrow the width

[rekon]

Hello

Please, tell me how to narrow the width of the forum? (content) and set some background?
For example, as is done here: http://hotspro.ru/forum/

 

[Jake Bunce]

Example:

https://xenforo.com/community/threads/wallpaper-size.22055/

That site is actually using max-width: 1200px; for their page width.

 

[rekon]

Thanks you)