Yes deepak you need to apply individually for NIT ,IP,DTU and NSIT.

NIT takes admission through JOSAA so by Josaa you can get into any NIT based on your merit. Counselling of NIT is centralised and is conducted by JOSAA/CSAB.

IP takes admission based on JEE Main score but through its own counselling done by IP itself.

Same is with the DTU and NSIT.

The JoSAA 2020 counselling will include steps like registration, choice filling, mock allotment, etc. Before appearing in JoSAA counselling, all eligible candidates have to register themselves and fill cllege and engineering straeam choices in order of their preference within the given deadline. JoSAA mock allotment result will assist candidates in modifying their preference of course and colleges. There will be seven rounds of seat allocation for all qualified candidates.

Candidates who qualify JEE Main will be eligible for NITs (National Institutes of Technology), IIITs (Indian Institutes of Information Technology) and GFTIs (Government Funded Technical Institutes). Candidates who have cleared JEE Advanced will be able to apply for admissions to all the 107 institutes participating in JoSAA counselling process including the IITs (Indian Institutes of Technology).

Hope it helps!