Update usage instructions, add links

README.md

@@ -8,12 +8,17 @@ It is written in Python and uses Qt for its graphical interface.
 
 # Dependencies
 
-Labelme requires at least Python 2.6 and has been tested with PyQt 4.8.
+Labelme requires at least [Python 2.6](http://www.python.org/getit/) and
+has been tested with [PyQt
+4.8](http://www.riverbankcomputing.co.uk/software/pyqt/intro).
 
 # 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.
+After cloning the code you should first run `make` to generate the
+resource file (a Python module containing all the icons).
+
+You can then start annotating by running `./labelme.py`. For usage
+instructions 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