If you are not a citizen of the country in which the IC3 Regional Forum is held, you may need a visa to enter the country. For more information on requirements and visa types, check with that country's embassy or consulate.
For IC3 Regional Forums in India, some nationalities can apply for an e-visa. Please read about the different e-visa types/options, eligibility, requirements, and the application procedures here: https://indianvisaonline.gov.in/evisa/tvoa.html.