Depending on your country of origin, you might require a Visa to enter Switzerland.
Detailed information is available on the official website of the Swiss Federal Department of Foreign Affairs. It might be helpful to contact your local Swiss embassy if you are not familiar with the process.
Official invitation letters will be available when registering for the conference.
Further information
More information is available here:
https://www.eda.admin.ch/eda/en/fdfa/entry-switzerland-residence/information-entry-switzerland-residence.html