Add usage to README.md

README.md

@@ -2,3 +2,19 @@
 A .NET client library for douban.fm
 
 **NOTE: This project is still under development.**
+
+## Usage
+1. Install [the nuget package](https://www.nuget.org/packages/Kfstorm.DoubanFM.Core/) to your project.
+2. Create an instance of `IPlayer` interface and call the methods. Here is the sample code:
+
+```
+    var player = new Player(new Session(new ServerConnection("02646d3fb69a52ff072d47bf23cef8fd", "cde5d61429abcd7c", "radio_iphone", "100", new Uri("http://www.douban.com/mobile/fm"), Guid.NewGuid().ToString("N"))));
+    await player.RefreshChannelList();
+    var newChannel = player.ChannelList.ChannelGroups[0].Channels[0];
+    var channelName = newChannel.Name;
+    await player.ChangeChannel(newChannel);
+    var currentSong = player.CurrentSong;
+    var title = currentSong.Title;
+    var url = currentSong.Url;
+    await player.Next(NextCommandType.SkipCurrentSong);
+```