Shubham, JEE Mains is the entrance examination for admission to NITs, IIITs, CFTIs and State Government run Engineering Colleges and Private Engineering Colleges. And few State Government run Engineering Colleges also conduct accept State level Engineering Entrance examinations. For example, KCET for Karnataka, GUJCET for Gujarat, etc. And all the seats are filled based on the marks scored and the rank in the merit list. You need not fill any form except for JEE Mains and the State CET application form based on the State you belong to.