When you first create a site with a new smarthub, you automatically become the site owner. To transfer ownership, go to "settings → site → transfer ownership".
To add a new user to your site, go to "settings → + others" and enter their email address. The person you added will receive an email in which they can accept your invitation, and create a user if they dont already have one.
As site owner you will have full access to all devices and their settings, as well as site settings, user access and more. Other users on the same site can either have full access or regular access, and the owner can change this any time. Users with full access can do all the same changes to the site as you can, and users with regular access can control all functions, but does not have access to settings.
In the Futurehome app you can administrate your user profile. By going to "settings → you" you can edit your name, phone number, email address and password.