Hello Kalyani,
You can find basic information about manual data entry in this training video:
http://www.youtube.com/watch?v=30u5_b9d5D4
You can find additional information in the EndNote Help file that can be accessed by clicking the Help menu and selecting Contents or EndNote X6 Help on the Mac. Here you can click on Entering and Editing References to find out more about how to manually add references to EndNote.