Hi Ostin Paul,

After completion of Engineering degree or while in final year of Engineering you can apply. you need to have a minimum of 60% marks.

Age limit- 20 to 26 years 

IAF Aeronautical Engineering sub branches:

1. Aeronautical Engineering Electronics

2. Aeronautical Engineering Mechanical.

Depending on your stream in Engineering you could join one of the sub branches. Here's the link to know more about the eligibility criteria,

http://www.careerairforce.nic.in/index1.asp?lid=34&ls_id=94&level=2&lang=1&pid=91

Good Luck!!