Hey Vivek !
If you got a college through Round 1 and are willing for Upgradation, then you need to the admission in the alloted college and then inform them that you are willing to sit in the Round 2 for Upgradation.
There won't be any need to appear for new registration but you would be needed to lock your choices again and submit.
If alloted a better college, you can pickup the documents from the previous one along with fees and submit in the freshly alloted college.

Good Luck !