To be able to make VoIP calls you need a VoIp account configured with your Zoiper.
If you do not have a VoIP account yet, you may review some providers here:
http://www.zoiper.com/en/voip-softphone/download/zoiper3/providers
Follow these steps to configure your VoIP account with Zoiper:
Go to Settings -> Accounts -> + -> select your account type (SIP or IAX) -> and fill in the information you received from your VoIP provider.
