Up to now I have not had any reason to use Gutenberg. As far as I am concerned the old editor was more than adequate. Gutenberg will still break older websites, and those websites have to use the old editor. In my searching around the web I have found a good primer about how to use Gutenberg.
Wpmu is a source of WordPress articles and this is the link to their post about how to use Gutenberg. https://premium.wpmudev.org/blog/a-tour-of-the-gutenberg-editor-for-wordpress/ While you are there be sure to check out their other instructions.
Here is a more comprehensive article about using Gutenberg. Go to ( https://www.codeinwp.com/blog/wordpress-gutenberg-guide/ ). Have fun.