For NIET there are a total of 2 admission procedures which are as follows.

On-campus: 

Visit the campus with your academic transcripts, i.e mark sheets of 1oth, 12th, etc. Let the officials know that you are interested in taking admission for CSE. You may have to take a test to do so. These tests are usually quite easy. Also, just a tip I got from my friends at the institute that good communication skills in English go a long way there. 

College Counseling: 

Clear a competitive examination, like AIEEE, UPTU with good rank and choose the institute for counseling. You can also select the college based on your Mains score. 

Here is the required UPSEE cutoff for CSE in recent years.

Hope this was of some help.