Divi doesn't currently include the option to put your site into an 'coming soon' mode. Fortunately, there are several plugins that will add this functionality for you.

Divi Coming Soon by Divi Life

Divi Coming Soon is a simple, and free, plugin that lets you designate a Divi Builder page as your coming soon page. This will then be shown to all users except admins / editors, who can see / work on the site. There is the option of purchasing pre-built coming soon layouts to go with it.

Divi Under Construction by Superfly

Divi Under Construction, like Divi Coming Soon, lets you designate a Divi Builder page as your landing page for non-logged in users. This premium plugin includes the ability to control access by IP address. It also comes bundled with several free coming soon page layouts.