In Order to get admission in Tamilnadu Engineering colleges, TNEA is the counselling process conducted by Anna University for the admission to undergraduate level engineering courses available at various engineering colleges of the state.  There is no entrance exam the admissions are based on 12th class marks. You can check the complete information about with the given below link.

https://engineering.careers360.com/articles/tnea

If you do not belong to Tamilnadu then other state students can apply through JEE Main Entrance Exam in private colleges Or the colleges like Amrita School of Engineering, Coimbatore, VIT Vellore etc have its own entrance exam.

You can check Tamilnadu Engineering colleges with the given below link.

https://engineering.careers360.com/colleges/ranking/top-private-engineering-colleges-in-tamil-nadu

Good Luck!