Hi Robert! That particular new feature does not have a topic on meta to accompany it yet, so we did not include a link for it. You can check out how it works by heading to /admin/customize/user_fields on your site and editing a custom user field.
Here’s an example of how a custom user field might be set up. Note the “For all users” option which, in conjunction with the other settings, will enable you to create new user fields that even existing users are required to complete before they access your site. This is great for when you updated your terms of use or privacy policy, etc.
Adding such a field will have a wide impact on your community so you’ll want to use it with care. A warning popup prevents you from doing this by accident! 
