After activating the theme, you will get a notification about installing the required plugins. You go to Appearance > Install Plugins to install them.
Please note that:
You don't directly purchase the Elementor Page Builder and Revolution Slider plugins. So you can not update them by yourself. It is also not recommended. When they have a new version, we will be careful to test and release the new theme version.
You should also not update other plugins without updating the theme. Please see our change log to make sure that the current theme version is compatible with the new plugin version.