Select "SIP Connections" on the left-hand navigation menu, click "+Add SIP Connection" and set up your Connection authentication mode and any expert settings you'd like. Now go to your number and add the Connection you just created.
You can also do this programmatically via our RESTful API. Check out our documentation for SIP Connections.
Here we'll show you how to set up your Opentact SIP connection, this will be necessary for features such as