Appearing or Passed class 12th you can apply for the exams:
JEE (Main+Advanced)- You can apply for this entrance exam  to take admission in IITs/NITs/IIITs and CFTIs. You should have 75% marks in your 12th class in order to be eligible or you should be in top 20 percentile. For SC/ST you should have 65% marks.

The other exams you can apply for B.tech programme.

 BITSAT

 SRM

 Manipal

  Amrita

 COMEDK

You can also apply in your state level entrance exam to take admission in state government colleges.

To check in detail about the entrance exam you can refer below link

https://engineering.careers360.com/exams

Good Luck!