Hi Akash!

The allocation of seats of through JEE MAINS/ADVANCE is done online. The allocation is done by a coordinating body known as JOSAA( JOINT SEAT ALLOCATION OF INDIA).

Where are seven rounds where the applicant has to fix or float a particular seat in any xyz institute of any branch. And there is an option where the student can finalise his/her seat at the very first round.  

After this the respective college calls the student for verification and admission.

hope this answers your query,

cheers!