VoIP settings can be found from Menu > Settings > Connectivity > Internet Telephone

You may get the VoIP call settings from your VoIP service provider via SMS message that you save in your device, or using the built in Internet telephone setup wizard by selecting Menu > Settings > Connectivity > Internet Telephone > Accounts > Add new (or Menu > Settings > Connectivity > Internet Telephone > Connect in some models). Alternatively you can configure the VoIP settings manually by creating them from the example configuration documents available at Developer Nokia, converting it to binary format and using OMA CP to configure them to the phone: 

http://www.developer.nokia.com/Community/Wiki/Nokia_Series_40_VoIP_Client_documentation 

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