Hello, 

If you want to get into Anna University after your 12th, you should apply for TNEA examination. Prepare for the examination. Attend it and then ace the test. Apply for counselling. Chose the college of your choice with a branch of your interest. Depending on your score, you'd land up in Anna University or it's affiliated colleges which you've applied for during the counselling. 

Coming to the eligibility criteria for applying, you should score above 60% to write the examination. There is a special quota alloted for students belonging to other states regarding the seats. Application is available online. You can find it in the official website.

Hope this helped you.

Thank you and keep asking :)