diff --git a/README.rst b/README.rst
index 1974510..15cfefc 100644
--- a/README.rst
+++ b/README.rst
@@ -34,6 +34,12 @@ Installation is equally simple::
     $ pip install flask-googlefed
 
 
+Prerequisites
+-------------
+Be sure that your Google Apps domain is enabled to be an OpenID provider under 'Advanced tools' > 'Federated Login using OpenID'
+
+Also, create the required federation end points on your domain. [See example](http://jeremiahlee.com/blog/2009/09/28/how-to-setup-openid-with-google-apps/).
+
 TODO
 ----