Hi Vijay,
This is one of the best places to get started with UI5.
https://sapui5.netweaver.ondemand.com/sdk/#content/Overview.html
The developer guide is pretty comprehensive, however I suggest you learn the Javascript fundamentals before looking at this. A good book is Javascript the definitive guide by David Flanagan.
Also this is a good post by Kevin Small to help get you going
Top 10 things ABAP developers should know when learning JavaScript
Also you posted this in the ABAP Space but you should probably have posted it into the UI Development Toolkit for HTML5 Developer Center
space.
Regards,
Katan
