This applies to Asynx Planetarium v2.80 and higher, if you use an older version, please update to the current version.
To add new locations, you have to find the geo coordinates. Search and find the location on the map, then COPY (mark it blue and Ctrl-C) the geo coordinates.
Go to Asynx Planetarium and open the location editor:
Mark an empty spot in the list, the new location will be placed there. Click the 'NEW' button.
Click on this field and PASTE (Ctrl-V) the previous copied coordinates:
Click the 'Check' Button. The coordinates are checked for the time zone and city name.
The coordinates were found. You can edit the location name here if you like.
You can also click any location in the list, then edit the details (like location name).
Click the 'SAVE and EXIT' button. The new location is now ready to use, just select it.