Add usage tips

README.md

@@ -10,6 +10,14 @@ It is written in Python and uses Qt for its graphical interface.
 
 Labelme requires at least Python 2.6 and has been tested with PyQt 4.8.
 
+# Usage
+
+After cloning the code you can start annotating by running `./labelme.py`.
+For usage help you can view the screencast tutorial from the `Help` menu.
+
+At the moment annotations are saved as a [JSON](http://www.json.org/) file.
+The file includes the image itself. In the feature support for XML
+output or possibly even [SVG](http://www.w3.org/Graphics/SVG/) will be added.
 
 # TODO