During the application form, you have no need to submit the EWS certificate. So if you are eligible for the EWS category then you can select the category- EWS. Now, you should apply for the EWS certificate by visiting the SDO office or district magistrate office, so that you can have the EWS certificate during the counselling or document verification of the counselling.

For more information regarding the JEE MAINS application form consider the link below:

https://engineering.careers360.com/exams/jee-main

I hope this helps. Wish you a great day!