How do I create a new custom field?

I looked through the previous topics so far, but unfortunately did not find an answer.

The custom post types section has a custom fields option that says “There are no custom fields here yet.”

Where can I create such unique fields that I can add to the listing?

For example: “event speaker” field group. Where I can get the speaker within a block, his position and say a quote from him.

Is there another way to create such a field group?