How can I allow users to add an event with a country and a city that I have not yet used at the backend? Currently, the dropdown lists restrict the places that can be entered to those that I have already provided via the backend. 

I am wondering how to add free text fields as provided here:
https://stachethemes.com/wp-demos/the-calendar/user-submission/

I have found the option that I had been looking for in General Settings -> Event Submission.