Modified: README.rst, added "how to install"

I have written explicit instructions explaining to inexperienced Pelican
users what must be done to use the themes in this repository. Changing 
the theme is the first thing I wanted to do after running the quickstart, 
but it took me a while of googling and reading existing Pelican 
documentation to figure out the (in retrospect, obvious) change I needed 
to make to my pythonconf.py.

README.rst

@@ -1,5 +1,61 @@
 Pelican themes
 ##############
 
-This repository contains themes for pelican, feel free to clone, add you own
+This repository contains themes for Pelican. Feel free to clone, add you own
-and make a pull request, it's community-managed!
+and make a pull request. It's community-managed!
+
+
+How to install a new Pelican theme
+##############
+
+These instructions assume you have already completed the Pelican Quick Start 
+guide at http://docs.getpelican.com/en/3.1.1/getting_started.html, have a 
+working blog, and would now like to apply a non-default theme.
+
+First, choose a directory to hold your themes.  For this example, I'll use the 
+directory :code:`path_to_themes`, but yours could be different.  Then clone 
+the :code:`pelican-themes` repository to your local machine.  
+
+.. code-block:: none
+	
+	$ mkdir ~/path_to_themes # or whatever
+	$ cd ~/path_to_themes
+	$ git clone git://github.com/getpelican/pelican-themes.git
+	
+Now you should have your :code:`pelican-themes` repository stored at 
+:code:`~/path_to_themes/pelican-themes/`.  
+
+Next use :code:`cd` to move to the directory where you are storing your Pelican 
+site.  To use one of the themes, you simply have to edit your 
+:code:`pelicanconf.py` file to include this line:
+
+.. code-block:: python
+
+	# Add this to pelicanconf.py
+	THEME = '~/path_to_themes/pelican-themes/theme_folder'
+
+So, for instance, to use the :code:`mnmlst` theme, you would edit your config 
+file to include
+
+.. code-block:: python
+
+	THEME = '~/path_to_themes/pelican-themes/mnmlst'
+
+Save :code:`pelicanconf.py`.  To see the changes, regenerate your site by using 
+the Makefile you should already have set up using :code:`pelican-quickstart`:
+
+.. code-block:: none
+	
+	$ make html
+
+Themes can also be specified directly using the 
+:code:`pelican -t ~/path_to_themes/pelican-themes/theme_folder` option.  If you 
+want to edit your theme, make sure that any edits you make are made to the copy 
+stored in :code:`~/path_to_themes/pelican-themes/theme_folder`.  Any changes
+made to files stored in your site's :code:`output` directory will be deleted 
+the next time you generate your site.
+
+
+
+
+