how to designate a digital legacy contact?

In the new iCloud terms, I saw the following:

Digital Legacy. With Digital Legacy, you can choose to add one or more contacts to access and download certain data in your account after your death. If your designated contacts provide proof of death to Apple and have the required key, they will automatically obtain access to that certain account data and activation lock will be removed from all your devices. Thus, it is your responsibility to keep your Digital Legacy contacts up to date. You can learn more about Digital Legacy at http://support.apple.com/HT212360 and  http://support.apple.com/HT212361.

However, both those links go to general Support. I cannot find instructions on how to designate a legacy contact.

The relevant support articles under "digital legacy" explain only how (as a legacy contact) you can request access to someone's account and how you can request deletion of a deceased person's account.