Open the theme customizer for the theme where you want to add the desired blocks.
Click on "Customize"
Navigate to the desired template.
Add a new section or block to an existing section, then click on the "Apps" tab to search for the desired Snap Block.
In this example, we're adding the "404" block.
After adding the block, explore all the available options in the block settings and adjust them to suit your needs.
You can customize the background and text color, add a background image, and much more.
Image picker.
Review all changes and save them when you’re ready to publish.