Hello,

Admission in Indian Institute of Science Education and Research is done through three channels

1. KVYP
2. JEE ADVANCED
3. SCB

You must appear in any one of these three exams and qualify in it. If you are applying through SCB channel you need to appear in the aptitude test conducted by IISER. For any other details you can click the link below

https://www.google.com/amp/s/engineering.careers360.com/articles/iiser-admission/amp