Finding Your Post Editor Settings
So, you have installed the praise worthy and all flashy, WordPress’ new Gutenberg editor and were enjoying the drag and drop features and wanted to use it as your default editor when you realized that you couldn’t find your Categories, Tags and Featured Image section… Doomed?
Worry not.. it is right in front you. Notice that little settings (gear) icon next to publish. It hides all that you need.
Just click on Settings and then Document, and you will get what you are looking for. After all Gutenberg is meant to be your default editor