You register for counselling and fill up choices of college for 1 round of selection. After 2 to. 3 days results of selection come. 
If you get any college you go to that college and either confirm your seat or ask for upgradation.
If dont them wait for second round
Next after 15 days results of second round will come and if get college then either confirm it or ask for upgradation
There is fresh choice filling for third round and if u get college u confirm it or else try next yr
Hope it helps u
thank u