Go to Virtual ports ‐> SIP folder and add there a new virtual port.

In popped window specify the SIP trunk name and choose in “Type“ parameter option “SIP Gateway“.

Then go to SIP Proxy and in bookmark “Stack” set parameters according to the picture below. Connect to the gateway – IP address of the opposite side (VoIP provider for example).
Register line – if your VoIP provider requires registration, activate this parameter and specify registration number.
Authorization data – specify a login and a password for authorization.
RTP interface – make a right mouse button click and add RTP interface.
Codecs – transfer required codecs from “Supported” to “Selected”.
DTMF according to RFC‐2833 – check this option for proper transmission of DTMF