Hi Richa.
For admission in Chanakya National Law University, Patna you will have to take the CLAT entrance exam which is conducted in May every year. The university accepts admissions only on the basis of your CLAT rank. The cut off for admission in this university was a rank of 909 in 2017 for the general category, hence you would require a rank around thid range to get admission in this university.
Best of luck!