Updated installation.rst, modules.rst and usage.rst.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>

docs/installation.rst

@@ -22,6 +22,10 @@ The enpt_enmapboxapp package is then installed into the QGIS_ Python environment
     On a Windows system, you have to activate the the QGIS environment first. To do so, run the OSGeo4W Shell (listed
     under OSGeo4W in the Start Menu) as administrator and enter ``call py3_env.bat``.
 
+To make the enpt_enmapboxapp GUI run together with EnPT_ (backend), EnPT_ has to be installed into a separate Anaconda
+environment. Please refer to the EnPT_ installation instructions
+`here <http://enmap.gitext.gfz-potsdam.de/GFZ_Tools_EnMAP_BOX/EnPT/doc/installation.html>`__.
 
+.. _EnPT: https://gitext.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT
 .. _EnMAP-Box: http://www.enmap.org/enmapbox.html
 .. _QGIS: https://www.qgis.org

docs/modules.rst

-enpt_enmapboxapp
-================
+API Reference
+=============
 
 .. toctree::
    :maxdepth: 4

docs/usage.rst

@@ -2,6 +2,20 @@
 Usage
 =====
 
-To use enpt_enmapboxapp in a project::
+The enpt_enmapboxapp GUI can be found in
+:menuselection:`QGIS 3.xx --> EnMAP-Box --> Processing Toolbox --> Pre-Processing --> EnMAP processing tools algorithm`
 
-    import enpt_enmapboxapp
+
+.. image:: ./images/sceenshot_how_to_start_1342x1029.png
+    :width: 1342 px
+    :height: 1029 px
+    :scale: 100 %
+
+Use the GUI to parameterize EnPT_ according to your input dataset and the desired processing settings. Before you start
+the processing chain, make sure, that the Anaconda root directory is correctly set. It should point to the Anaconda
+installation containing the previously installed `enpt` Python environment.
+
+The status of computation can watched in the log tab and the QGIS Python console.
+
+
+.. _EnPT: https://gitext.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT