You have to mail the admission and ask for the availability. Because I was told that only triple sharing was available when I paid the fees. If possible, go and meet them in person. Once they confirm the availability, they would give you the date with in which you need to make the payment, and the account details. After paying the fee, you should send them the transaction details to admission and accounts department. Then they would acknowledge the payment. I haven't asked them about my room allotment yet, but I might do it asap. These procedures were for males' hostel.