You need to appear for National level exam like IIT JEE or you state level Engineering exam, according your score you can go for B.tech college with CSE or IT branch to become a Software Engineer. To get admission in IITs, NITs, IIITs or GFTIs you should have minimum 75% in class 12th as a general Category & 65% as a reserved category.

You can check the eligibility to appear in IIT JEE:

• 0+2 or any equivalent exam, conducted by any recognized Central/ State board like CBSE, ICSE, Council for the Indian School Certificate Examinations, New Delhi etc.

• Intermediate or Pre-University Course or Pre-Degree Course examination conducted by a recognized Board/ University.

• Final examination of the 2 year course of the Joint Services Wing of the National Defence Academy.

• Vocational examination of H.S.C.

• National Institute of Open Schooling conducted Senior Secondary School Examination with a minimum of 5 subjects.

For further information about you can go through with given below link.

JEE Main Eligibility

In order to become a software engineer you have to complete your B.tech and you can take CSE branch and  you have to appear for the entrance exam like- JEE, BITSAT, SRM, VIT, Amrita and Manipal.

To have an idea of entrance exam you can refer below link

List of Engineering Exams

In order to take admission in top colleges like NITs/IITs/IIITs and GFTIs make sure you get 75% marks in your board exam or you should be in top 20 percentile.

Below are the top colleges for CSE you can check below

• IIT Bombay
• IIIT Hyderabad
• IIT Kanpur
• IISc
• NIT Trichy
• NIT Warangal
• IIT Kharagpur
• BITS Pilani
• DTU
• NSIT

Good Luck!!