The whole thing is very simple:
1. If you are logging in for the first time, sign up first.
2. After registering and clicking on the link that was sent to your mail (which you used during the registration), you will return to the registration window - enter your login details on the right side (you can use this data every time you want to log in, or save your password).
3. After logging in, you enter a virtual game space, which is open from the 1st of June until 31st of August. Enter at least one active minute in the Strava app (be sure to make your profile public and indicate the intensity of the activity) and you're already participating in the Project!