You may get the VoIP call settings from your VoiP service provider via an installation message that you save in your device, or you can create the settings yourself with a separate tool program (e.g. SIP VoIP Settings).
In Symbian^3 devices, when an internet call service has been installed, a tab for the service is displayed in the Contacts menu.
When you are signed in to an internet call service, you can make a call from the friends list or the contacts list. Select Menu > Contacts.
To call a contact in the friends list, open the internet call service tab, and sign in to an internet call service. Select a contact from the friends list, and select Internet call.
To make an internet call to a phone number or SIP address, in the home screen, select Call to open the dialler, and enter the number. Then select Options > Call > Internet call.