Sahil, If you appeared for the January JEE MAINS with category status as general and had not registered your category status as OBC and want to change your category for April JEE MAINS, then you have to register for the April mains as a fresh candidate by entering all the details asked in the application form from the start and enter your category sttus as OBC. The candidates who want to apply for April JEE using the same personal credentials as that in Jan session, need not to register themselves as a fresh candidate and they can apply for April JEE bycarrying forward the same details, however, if you wish to change your category or use your OBC Certificate,if you have got it issued, then you would have to register as a fresh candidate for April JEE MAINS and NTA would treat you as a new candidate.