First of all, please note the following when using this feature:
The "Protected Sign-On" does not increase the security of a login as the term may suggest.
In addition to that, this feature is only relevant if you are working with an Enterprise Server database. Besides, it is only useful if the administrator allows you to access an entry, however, you are not permitted to see or edit the password itself.
If you still want or have to log on to a website, this can only be realised using the "Protected Sign-On" feature. In this case you can log in on the requested website but cannot see the entry's password in plaint text.
Modern browsers such as Chrome or Firefox cannot be controlled by third-party applications like Password Depot thus, the Internet Explorer is always used for this purpose exclusively. Please note, that this is always the case regardless of your global browser settings (Edit -> Options -> Browsers -> Default browser) or the browser settings of individual entries (Password -> Properties -> Additional -> Preferred browser).
To use this feature, it is required installing the Internet Explorer on your device.