Hello Rahul,

To get a seat through CSAB counselling you have to be first JEE Main qualified and should have a valid rank in JEE Main. Now as per your rank, you may have a chance to appear for CSAB counseling. For CRL category the JEE Main cutoff is 89.75 percentile. If you have achieved more than than that, then you are JEE Main qualified and hence rightfully eligible for CSAB counselling. CSAB counselling will begin just after the completion of JoSAA counselling and through this you can get seats in NITs,IIITs,GFTIs,SFTIs. 

You can go through this link and checkout the details regarding CSAB counselling : https://engineering.careers360.com/articles/csab

Good Luck!!!