Added documentation on how to setup the QTH pinpointing functionality.

docs/source/getting_started.rst

@@ -20,7 +20,7 @@ Installation and running
 ------------------------
 
 Assuming that the current working directory is PyQSO's base directory
-(the directory that the Makefile is in), PyQSO can be installed via the
+(the directory that the ``Makefile`` is in), PyQSO can be installed via the
 terminal with the following command:
 
 .. code-block:: bash

docs/source/toolbox.rst

@@ -36,7 +36,9 @@ Grey line
 
 The grey line tool (see figure:grey_line_) can be used to
 check which parts of the world are in darkness. The position of the grey
-line is automatically updated every 30 minutes. The user's QTH can be pin-pointed on the map by specifying the latitude-longitude coordinates in the preferences.
+line is automatically updated every 30 minutes.
+
+The user's QTH can be pin-pointed on the map by specifying the QTH's location (e.g. city name) and latitude-longitude coordinates in the preferences. If the `geocoder <https://pypi.python.org/pypi/geocoder>`_ library is installed then these coordinates can be filled in for you by clicking the lookup button after entering the QTH's name, otherwise the coordinates will have to be entered manually.
 
    .. _figure:grey_line:
    .. figure::  images/grey_line.png