The bachelor of architecture  courses offered at both NIT and IIIT but not in all NIT and all IIT that is only few NIT and  IIT which offer this course.

To take admission into Bachelor of architecture at NIT you need to appear for JEE Main paper 2 and get a good rank and based on your rank in JEE Main paper 2 you will be offered Bachelor of architecture course at NIT.

To take admission in DTU Bachelor of architecture course at I which offer it you need to first appear for JEE Main paper 1 and qualify it and then you will be eligible to appear for JEE advanced then you need to appear for JEE advanced and qualify it with a good rank and after that you need to register for architecture aptitude test and qualify IT which is conducted by IIT then only you can take admission into Bachelor of architecture course at IIT.

Hope this helps all the best.