3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone.
3CXPhone can be obtained from the 3CX website.
Installing 3CX VoIP Phone is easy and only takes a few minutes.
Click on Set Up/Configure Account. Click on New.
Ensure I am in the office - local IP is selected, and enter the hostname or IP address as provided to you in your welcome email.
Click Advanced settings toward the bottom of your SIP Account settings window to set advanced options.