Hello,
"I have Instantiate my custom object. Now to which variable I have to map this custom object and how i can use display method to write code as Call transaction xyz."
You can give the object instance container element any name you want.
When the user clicks on the link (that is created when you instantiate a BOR object) then the default method for that object will be run. That is usually the Display method but you could possibly change it to something else, e.g Call Transaction.
regards
Rick