Add Usage section to readme.

README.markdown

@@ -13,6 +13,19 @@ While shuffling bytes between the incoming browser and the outgoing server, fake
 
 E.g. for automated testing, the [LocalhostInterceptor][2] can route browser traffic that would otherwise go to `http://www.somesite.com` to `http://localhost`. This is useful for containing (and asserting against) URLs within your application you either cannot easily change or are using to test cross-domain functionality.
 
+Usage
+=====
+
+Run [Proxy][6] as the main class, passing in the port as the only argument. Or with the jar:
+
+    java -jar fakehttp.jar 8081
+
+The fakehttp jar includes its own dependencies (netty and the Scala runtime library) to make copying/installing it easier.
+
+To change things other than the port (e.g. interceptor or ssl mode), currently you just have to edit the [Proxy][6] class.
+
+Note that you'll also have to configure your browser to use the proxy on the host/port you started fakehttp on.
+
 SSL Modes
 =========
 
@@ -31,3 +44,4 @@ fakehttp is Apache licensed, except for the CyberVillain stuff that drives [Clea
 [3]: /stephenh/fakehttp/blob/master/src/main/scala/fakehttp/ssl/OpaqueSslMode.scala
 [4]: /stephenh/fakehttp/blob/master/src/main/scala/fakehttp/ssl/ClearSslMode.scala
 [5]: http://code.google.com/p/selenium/source/browse/selenium-rc/trunk/server-coreless/src/main/java/cybervillains/ca/CertificateCreator.java
+[6]: /stephenh/fakehttp/blob/master/src/main/scala/fakehttp/Proxy.scala