Internet Facing Deployment refers to a deployment of Microsoft Dynamic CRM where the service is provided by a reseller or service provider and the Dynamics server is accessed via login through a web page.
When logging in to an IFD Dynamics server you typically use an e-mail address (or an e-mail address like username) for your username and a password provided by the service provider. This is not the same username and password (credentials) that you use to login to the Dynamics server using Flexor.
In order for PC software, such as Flexor CTI, to connect to an IFD Dynamics server it is neccessary to use something called SPLA (Service Provider License Agreement) Authentication. As stated above the credentials for SPLA are not the same as those you would use for logging in to the Dynamics server via a web page.
In order to login using Flexor with SPLA Authentication you need to ask your service provider or company hosting Dynamics for an SPLA login for your Dynamics account. They should provide you with a Username, a Domain and a Password (the password is likely the same as your IFD password). Using these credentials you can log into Dynamics using Flexor or the Flexor Dynamics Configuration Tool using SPLA Authentication to set up or use Dynamics with Flexor CTI.