Hi

First of all, as per eligibility criteria, you need to pass your class 10 examination , with at least 35 percent in science and maths subjects.

Then you need to appear for college level or state level entrance examination for getting into diploma college, for example , in Jharkhand you need to appear for entrance exam called Jharkhand polytechnic exam and then admission is provided based on rank in the entrance exam.
Many colleges also provide admission on the basis of Marks obtained by you in class 10th.

Thankyou