The EWS category stands for the economically weaker sections of the society. To apply for this category, there are different criteria made in different states as well as different educational institutions. If you want to apply, you will have to produce an income certificate (which is the official record of your family's monthly or yearly income). If your income fits in the criteria, only then can you apply for the EWS certificate. Moreover the EWS certificate is for candidates not covered under any reservation provided by the government but are economically backwards.