Hello Dhana,
There are various venues to do that and it really is a matter of preference.
I personally prefer the online help available here:
http://help.infragistics.com/NetAdvantage/NET/2008.2/CLR3.5/
But if you have installed the product locally, you will be able to access that locally as well.
I also find the following resource to be of much help:
http://devcenter.infragistics.com/Support/KnowledgeBase.Aspx
Here, we have thousands of KB articles for our products in real-world situation, often with sample code and even projects attached.
Finally, recently I have found the Forum Search to be a very powerful tool, since we now have more than 40,000 posts - so if you try a search in the forums, the way you do in Google, chances are you will land on the answer right away.
Of course, if you do not find the information you need - just ask us - we will gladly help.