Using Blank Page template
The Blank Page template doesn't have default header and footer. When this template is enabled you can create custom header and footer using sections and modules of the Divi Builder.
Once you have done it you can save sections to the Divi Library and load them on other pages.
Using 3rd party plugin
You can find a few plugins that will help to create custom headers and footers. Here are two plugins.
Note: these plugins are not our products and we cannot guarantee support with them. These plugins are created by 3rd party developers, if you have any questions regarding how they work you will need to reach out to the plugin developers.
Changing code of the theme
To change default header and footer you will need to edit code in header.php and in footer.php files. If you are familiar with HTML and PHP you can any type of header and footer that you need.
Another option is using the shortcode of the Divi Builder. Here is the tutorial about how you can generate the shortcodes of the sections and modules. Using the
do_shortcode() function you can display the modules in template files.
To see how it works you can generate the shortcode and place this code to the very top of the footer.php file
<?php echo do_shortcode('[ADD DIVI SHORTCODES HERE]');?>
Note: If you modify any template files like the footer.php without a Child Theme then you will lose those changes upon updating. To create a child theme you can follow this tutorial.