For any information concerning the visa for Switzerland, please refer to the official website of the Federal Department of Foreign Affairs: Visa requirements (admin.ch)
Please note that the Organising Secretariat can only provide you with an official letter stating that your registration and accommodation are confirmed upon receipt of payment. The Organising Secretariat will not be able to help you with the visa procedure itself. Each participant is responsible to contact his/her embassy to set the information.
Please make sure that you start the procedure soon enough to have time to provide the requested documents and have your application approved before departure.
Up-to-date information on entering Switzerland during the COVID-19 pandemic can be found here: Travel (admin.ch)