To get admission in NITs in MCA program, you will have to crack NIMCET exam as this is the basic eligibility criteria to get seat there. Also, candidates qualified with B.Sc./B.Sc.(Hons.)/BCA/BIT under 10+2+3 pattern with Mathematics/Statistics as a subject or equivalent are eligible to apply for the same.

And for 2018 session, the registration is going on till 31st March and exam will be held on 27th May.

For reference, you can go through the below links -

https://it.careers360.com/articles/nimcet

https://it.careers360.com/articles/nimcet-eligibility-criteria 

Good Luck!!!