Updated README to have instructions.

README

@@ -8,4 +8,33 @@ This does not (currently) have a proper Python ``setup.py`` script for installat
 since this is such a random mixture of components.
 
 It's probably best to include a ``.pth`` file in your ``lib/site-packages``
-that references this working directory.
+that references this working directory.
+
+Installation
+============
+
+First, set up your path. Put the path to this directory in a tigershark.pth file
+in your site-packages directory. Eg:
+
+    cd /home/me/envs/my_project_virtual_env/lib/python2.7/site-packages
+    echo "/home/me/envs/my_project_virtual_env/src/tigershark" > tigershark.pth
+
+In order to process X12 files you first need to generate a parser from the xml
+or cf that describes the file format. The PyX12 package includes xml files for
+several common file formats, which is included in the Download directory:
+
+    cd Downloads/
+    unzip pyx12-1.5.0.zip
+    cd ..
+
+After extracting the xml files, you can create the related parser objects
+using the utlities:
+
+    mkdir parsers
+    touch parsers/__init__.py
+    cd parsers
+    python ../web/make837.py -p M835_4010_X091_A1.py -b Downloads/pys12-1.5.0/map name=835.4010.X091.A1.xml
+
+This will generate a M835_4010_X091_A1.py file in your parsers directory.
+
+TODO: Still need a Factory?