Connection parameters for SIP "trunking" provider

Referencing p 176 of the definitive Asterisk guide, 4th ed, I’m trying to configure for babytel like so:

article.gmane.org/gmane.comp.tel … ser/58888/

how do I specify:

SIP Proxy: sip.babytel.ca
SIP Proxy port: 5060
Outbound Proxy:3 nat5.babytel.ca
Outbound Proxy port: 5065

in sip.conf?

As per their directions:

I modified the /etc/hosts file. Not sure it was necessary, but I did as suggested above.