I'm new to CRM , now i just want to add a sample button named as sample in Ribbon, i have exported "customized XML" , from here how to add custom id , command id etc.
There are a couple of walkthroughs which should be able to help you with this:
There are also tools like this one on CodePlex which can help you do it in a graphical fashion rather than messing with the XML.
Warning, opinion ahead
I remember when I was new to Dynamics CRM that what helped me initially was working with tools from the community until I got my head around things and could dive into more of the guts of the platform. It might be worth going through a listing like this to see if there are things that can help you on your CRM journey.