Pay attention that the Olympus theme has 2 possible demo contents. The first is build on Elemntor, the second on WPBakery page builder. Check out this doc for more details Demo data import.
Many customers get confused when the WPBakery plugin is not installed automatically with the demo data for Elementor. Please, note that depending on which demo data you chose, the same plugin will be installed automatically.
The WPBakery Page Builder is included in the theme package in any case. However, it won't be installed automatically unless you imported the demo data built on WPBakery.
If you installed the demo data for Elementor, you can find the 'js.comoser' file at the 'Theme Plugins'folder inside the theme package, which is the WPBakery page builder plugin:
Then you can upload it manually under Plugins > Add New:
As well as that, you can have this plugin installed automatically if you installed the demo data for WP Bakery under Tools > Demo Content Install: