How to post background behind centered page

[bancroftconstruction]

i have created a website and posted it centered in the browser. i would now like to post a background that would cover the entire browser page with my site centered over it. how would i go about doing this? for an example see balboamediagroup.com. i was thinking something similar to this. thank you in advance for your help.

dustin

https://www.bancroftroofing.com

[davidundalicia]

Re: How to post background behind centered page

Page properties - background - Image