Hello,
You mentioned Pcmb means you had mathematics and biology both then you can make IIT by giving JEE main and advance entrance exam.
Some private colleges offers engineering on the basics of 12th marks and some colleges take their own entrance exam for engineering.

All the best!

Hello student,
To procure a seat in the IIT's, one should first appear for the JEE main examination. After this exam, the cut off's required to be eligible to JEE advanced exam will be released according to your category. So, if you qualify mains,  you can go for advanced. Scoring high in mains gives you a chance at the NIT's, IIIT's and GFTI's. If you score high enough in JEE advanced, it will land you in IIT's.
Good luck