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 Container sub-option is the first in the list of this section.
The ‘Container’ section lets you adjust the Container Width and the Container Layout.
This setting will set the width of the container for your website content in pixels.
The default is set at 1100px and is usually fine for most websites.
There is a lot of discussion about what is the ‘best’ width depending on your content and how you think people will view it, so I will leave it up to you to ‘google it’ and see what will work best for your website.
This setting will put a border around your content if you choose ‘Separate Containers’ and merge your containers into one if you choose ‘One Container.’
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 Container options for your website using the Customizing feature in WordPress.