I had been hearing a lot about XPages Extension Library and finally got to try it out in XPages code-a-thon held at Mumbai. So I decided to try it on my local machine along with little help from experts on StackOverflow. Its a simple two-step procedure - install extension library and run extension library.
Install XPages Extension Library
First of all get the latest release of extension library from OpenNTF. Unzip the file and find "updateSiteOpenNTF-designer.zip". Unzip it and you will get two folders of "features" & "plugins" and a file "site.xml". In Lotus Notes sidebar, go to My Widgets and select "Options > Configure a Widget from... > Features and Plugin on an Update Site". If you are unable to see My Widgets in your sidebar then click here.
Now enter the URL for the update site as: file:///C:\
After you are done installing restart the Notes client. Then you would be able to see the extension library components in your Controls tab in Domino Designer.
Running XPages using Extension Library components
If you try to preview any XPage which uses extension library components then you would get an error as Cannot find the library com.ibm.xsp.extlib.library, required by the application
For that go to