It is currently possible to register 30 days in advance.

If you want to attend only the recovery, simply join an hour late, at 09:55 (Germany time).

You will be let in at the full hour.

The link will be sent to you per email. Some email programs hide the link under "view full text".

Also look in the spam folder if you are not receiving it after 10 minutes, then add sumna to your address book to ensure future delivery.