If you are using the GeneratePress Theme and have uploaded the Add-Ons plugin and activated all of the options, the Layout option is the third section you’ll see when you click on the Customize link from a page or post.
The Header sub-option is the second in the list of this section.
The ‘Header’ section lets you adjust the Header Width and the Header Alignment.
This setting will set the width of the header of your website.
If you choose Full from the drop-down menu, the header will be full-width.
If you choose Contained, the header will be in a box. Its appearance will be controlled by other customization options.
This setting will adjust the alignment of the content of the header.
The options are Left, Center, and Right.
Once you are done making your changes, click on the Save & Publish button at the top of the Customizing sidebar.
If you change any of these options while you are in the Customize mode you will be able to see how the change affects the look of your website.
Congratulations! You just set the Layout Header options for your website using the Customizing feature in WordPress.