For B.tech CSE branch to take admision in top colleges you have to prepare for JEE Exam.

Below are the top exam for engineering admission (2017)

1- JEE Main

2- JEE Advanced

3- BITSAT

4- VIT

5- SRM

6- Amrita

7- Manipal

You can also apper in your state level exam.

To know in detail about the exam you can refer below link

List of Engineering Exams

Good Luck!!