hello aspirant...

for admission for architecture in iits..

you will have to appear for both the jee mains paper1 and 2 and you should qualify in both the exam. After that you should appear for the jee advanced examination and you should also qualify in it. then you can  apply for the architecture advanced test (aat). It is based on this rank the admission of iits for architecture takes place.

hope this helps

all the best