Hi aspirant

You can check official websites of the univerisities .You need to research a bit .As the process may vary from university to university.You need to visit the admission section of the website of different universities .There you can check the process,eligibility criteria etc.

You can apply to NITs/IIITs/GFTIs through centralised counsellig i.e CCMT

And you need to apply individually to all IITs .They don't have centralised counselling.

Hope this was helpful.