how do I disable the firewall through yast?

the fine manual states:

The Start-Up section defines how your firewall will start. You can either have the firewall start automatically when booting (recommended), or you can set the firewall to start manually. You set this by clicking on the appropriate radio button for these two options.

How do I know whether the server itself has a firewall blocking port 5060?

linux-k7qk:~ #
linux-k7qk:~ # netstat -anlp | grep 5060
udp        0      0 0.0.0.0:5060            0.0.0.0:*                           3548/asterisk      
linux-k7qk:~ #

I'm using yast, and looking in network card setup, and the more general "network settings," but cannot find a "firewall" tab...

Because other computers on the network are able to call out with SIP, I suspect the firewall on the server itself is causing problems and not allowing clients to connect.