Hello @emolotel
If you are using the free or the professional version of the plugin, you can insert a DropDown field and enter every city as a choice in the field, however, if you use the Developer or Platinum version of the plugin you can insert a “DropDown DS” field and populate the list of cities from a CSV file or database. More information in the following link:
https://cff.dwbooster.com/blog/2019/02/14/ds/?index=1#csv-file
Best regards.