Deepak, it is possible to change your category for the April JEE MAINS but if you want to do so, then you have to leave aside the credentials entered for Jan session JEE and apply again as a new candidate.National Testing Agency (NTA), the conducting body for JEE MAINS allows the change from one category to another, say from General category to EWS as in your case, by filling the application form for April JEE as a fresh candidate. So, if you want to change your category in April JEE MAINS, then you would have to register as a fresh or a "new" candidate by entering all the asked details from the starting. The registration process for April session is easier for the already registered candidates who don't want to change the credentials and carry forward the same credentials entered for January JEE but if you have to change the credentials or details,you have to register yourself as a fresh candidate by going to the application portal and clicking on the link "fresh applicantions only" and register by entering all the details asked and enter your category as you wish. But remember that you should have the proof of the category you enter, otherwise you may land into problems during the counselling process. If you do so and register yourself as a new candidate, then you can give the April Mains as an EWS candidate and NTA would recognise you as a "new" candidate.