Can't connect to the sip trunk.

[madsam]

I have set up a sipx pbx and have phones registering to it. But when I try to connect the pbx to the sip trunk, there is no place to put the password to authenticate to the siptrunk.

Where do you put the password in to the sip trunk gateway?
Do you have to use a different type of gateway?

I found a statement "Authentication is done at the TLS connection level."

If that is true, where is the documentation on setting up the TLS layer?

Thanks for your help.