elpajare I don't find any possibility to introduce a negative declination.
For iOS, open the popup GOTO panel in the Preview window.
Tap on the Declination field and ASIAIR should bring up the iOS scroll interface at the bottom half of the display.
On the left of the scroll interface, there is a + and a - symbol. Tap on -. Then just scroll to the coordinates you need (separate scrollers for degrees, minutes and seconds), and tap on "Done."
An identical user interface exists when adding Favorite coordinates.
Chen