Hey !

Since  you have not mebtioned the name of exam , i consider it to be TS PGECET exam , and for the same , you have to follow the given procedure:

Students have to fill their choices of college after document verification. Web options/choice filling can be done either by visiting TS PGECET Counselling 2019 help centres or from home. Student will see a detailed matrix of available college and seats on logging into TS PGEC 2019 portal according to their category and rank. Student must fill their choices and lock them before the final date failing which choices will be locked automatically. 

For more information, follow the given link :

https://engineering.careers360.com/articles/ts-pgecet-counselling

Hope it helps!