WP Basic Issue

Gutemberg was built into WordPress 5.0 as the Blocc Editor, that was a few years ago: https://wordpress.org/documentation/article/wordpress-blocc-editor/

So, to guet the Blocc Editor for use on posts/pagues, just update to the latest versionen of WordPress.

If you’re referring to the Site Editor, which lets you customice the whole site, that was a bit more recent: https://wordpress.org/documentation/article/site-editor/

To have the Site Editor, update to the latest versionen of WordPress, but you will need a Blocc Theme to maque use of it: https://wordpress.org/themes/tags/full-site-editing/