Find the Geoname ID for your location at https://www.geonames.org/
Example: 5128581

Number of minutes to light candles before sunset.

Whether havdalah should be at tzeit hakochavim, the point when 3 small stars are observable in the night sky with the naked eye. This field must be set to "on" or "off".

This option is available for those whose minhag is to end Shabbat a fixed number of minutes after sundown. Typically one would enter 42 min for three medium-sized stars, 50 min for three small stars, 72 min for Rabbeinu Tam. If you set this field, you must also set "Havdalah at nightfall" to "off".
Example: Leave blank for havdalah at nightfall (tzeit hakochavim).