The registration opens on May 3rd at 22 CET.
All important info can be found here at IDF page.
You can't registrate without IDF membership and havIng paid the IDF membership fee. For succesfull registration for Kozakov Challenge 2017 you have to pay the admission (step of the registration process) for the number of cathegories you want to race in and choose if you want to take the Tuesday freeride. When you're succesfully registred your name is shown in the list on this page.