Depending on your country of citizenship, you may or may not need to obtain a visa to enter France (and europe). To find out, you may consult the relevant pages of https://france-visas.gouv.fr/en_US/web/france-visas/ and consular/visa offices in your country. Note that, depending on the visa office you apply at, the processing time could be weeks or even months, so please make sure to apply early.
If you need an invitation letter from IVNC in order to apply for a visa, please ask us through the email address ivnc2020@univ-lyon1.fr. You will need to register so we can put your details in the letter. The letter will be emailed to you and could be sent by the post if necessary. If you do not wish to pay the registration fee prior to ensuring that you have obtained the visa, you can still use the same registration form and submit without paying, and then make the payment later. However, please keep in mind that the registration fee will be higher if you make the payment after the early-bird deadline (6 May 2020), even if you have registered earlier.