Hye Jagwani,

Nirma University offers only MBA course, it does not offer PGDM. And for the entry the candidates have to appear for Common Admission Test (CAT). After appearing for the CAT, aspirants should apply to the Institute for admission. Nirma University will get the CAT scores of applicants directly from IIM's and return call you with an offer letter, if they find you eligible.

Other than through CAT you can also apply through GMAT. 

XAT score is not considered here, so you better appear for any of the above exams. As you cannot appear for CAT if you are planning to join this year. GMAT is your best option.