Upgradation is among the seats you have locked in the first round of counselling.

For example, you have given 6 college choices according to you prefernces and have been allotted the 5th college in round 1 of the counselling. If in the round 2 of seat allotment if a seat is available in the more highly preferred college then your seat will be allotted in that college.

If you are not allotted a seat in first round on the basis of your rank, and therefore you are not participating in the first round, you can directly participate in the second round.

But if you are allotted a seat in the first round, it is necessary to take admission there then you will be eligible for second round.