After the B.Arch exam is over, NTA will allow you to download your responses and the answer key (by NTA) after a gap of some days post exam. In the same way, after the exam for April attempt is over, NTA will announce the final result (considering the best out of the two) by 31-Apr-2020.

After this, you will have to wait till the results of JEE Advanced are out irrespective of whether you appear for it or not. Thereafter a national admission conducting body, JoSAA invites applications from the candidates willing to enroll themselves in any IIT/ (NIT/IIIT/CFTI) based on the scores of JEE Advanced and JEE Main respectively. There you will have to register yourself and fill the choices of the institutions and the courses you wish to get enroll in. Admission will be based upon the results of the exam and the availability of the seats in the respective institution for a particular course.