add installation chunk

jass_preprocessing/doc/source/index.rst

@@ -30,6 +30,20 @@ The QC and preprocessing step goes as follow:
 | rs6548219| 30762 | A	  | G   | -1.133 |
 +----------+-------+------+-----+--------+
 
+Installation
+============
+
+In a folder that will contain the jass_preprocessing repository,
+execute the following lines:
+
+.. code-block:: shell
+  git clone https://gitlab.pasteur.fr/statistical-genetics/JASS_Pre-processing.git
+  cd JASS_Pre-processing/
+  pip3 install ./jass_preprocessing/
+
+
+
+
 Preprocessing example
 =====================