Hello !
If you have added a backgroud color / image then your website will be in a Boxed view.
In order to make the site full width you have to select every row of your page using the tagDiv Composer and then set the stretch mode you want like here : https://www.screencast.com/t/BkWwdHh6
In order to make the post page full width you will have to add a single post template and then edit it. Check more about how to have single post template here: https://tagdiv.com/customize-articles-with-single-post-templates/ And for the header you can do it here: https://www.screencast.com/t/xf56tQN0.
These are the ways you can increase your page width from theme options. Anything above this will require custom code.
Let me know if this helped you !
Thank you !
