Hi NIFTEM takes admissions through JEE Main scores. NIFTEM will announce the dates for admission. You will have to apply directly to NIFTEM when they open the admissions mostly in May, register, pay Rs 1000 as application fee and upload your photo as well as signature as specified. Admissions are on the basis of the JEE Main ranks so obvisoly you must qualify in JEE Main and get a good rank.

If you want to check the details, the last year's brochure gives it all - http://niftem.ac.in/upload/Admission%20Brochure_2017-18.pdf