Hello Dhanush 

The easiest way to admission in NIT is that you need to register in JoSAA . They will offer you seat in the college where  your marks is applicable. For getting  admission in architecture, it depends on the college for which you need to be award of the criteria of admission for a particular college.  If you score 250 , you will get admission. And registration for JoSAA will start from third week of June . Then they will give you the list of college which you can choose of your choice . Stay alert and check the notification from JoSAA so that you get admission on time 

Hope this information clarify your doubt . Thank you