Dear student, thanks for your question. To get into IIST YOU have to score very good marks in jee advanced. To briefly say for a General category student 75% in your 12th board examination is must and you must score at least 20% of jee advanced 5% from each subject is minimum and these scores are taken into account so as to shortlist you for the admission process. There will be limited seats for each branch .To get to know the complete information please go through the following link.

https://www.iist.ac.in/admissions/undergraduate