Hello!

To qualify for appearing the JEE advanced examination, you need to qualify the JEE mains exam first

The rank list will  e out for the JEE mains exam in which you will know from your rank in general and category,  that you have qualified or not.

If you have, that is your percentile is above tge cutoff percentile, you will  be eligible to apply for JEE advanced. Moreover,  when the form is released you will certainly get to know it cause it will be available for applicants to apply on net.

Hope this will clear your doubts.