To learn OOABAP step by step go thru the below SDN link.
The below pdf link from sap press will give you an insight of Abap objects.
You can also go through the transaction: ABAPDOCU for getting the examples.
Also go through the below blog by Thomas Jung on OOABAP Programming
Hope the above links will be useful for you to start with the basics of OOABAP
All the Best.
I guess you are new to the forum. This is a forum for SAP CRM Service. You would better post your question regarding ABAP Objects in ABAP Development--> ABAP Objects Forum. Also please go through the rules of engagement and try restraining yourself from posting such basic questions.
Search the forum. It has a wealth of information.
Hope this helps.