Your school can help you enroll for the International English Olympiad (IEO). The Science Olympiad Foundation (SOF), the organizing organization, accepts student submissions submitted on behalf of their schools only. If your school is listed with the SOF, you may thus pick up application forms from there. You must fully complete the application form and pay the INR 125 registration fee.
Additionally, your institution could charge INR 25 for additional costs, instructor assistance, an honorarium, etc. If your school wants to participate but hasn't registered with the SOF yet, it can do so by getting in touch with the SOF by phone or email.