First, HES admin has to order as many SSO licenses as many users will use Hideez Authenticator.
Administrators can log into the HES service and use the SSO service by default, but employees with user accounts cannot, so they first must have an explicit permission of the administrator:
Select an employee and click the 'Edit' button.
Then click the 'Enable SSO' button at the opened page to give the permission.
If you want to require Hideez Authenticator as a second factor, check the "Required Two Factor Authentication" box and then click the "Enable" button.
If you want to allow user use passwordless authentication with the Hideez Authenticator, don't do it, just click "Enable" button.
Also, you can enable SSO and the second factor for the user during the employee creation on the “Single Sign On” step: