The process is called Free exit. It means when a Candidate has been allotted a seat and even if the Candidate does not report/join the allotted college he/she would not be penalised and will be eligible for subsequent round. So there is no process per se. You don't have to report to the allotted College. And that will be considered as a free exit. But if you haven't been allotted a seat in Round 1 and do not further wish to continue with further rounds, you simply do not have to participate in Round 2 and mop up rounds. Your security deposit will be refunded after all the rounds of counselling are done.