Hi. Third party server. SIP. Thank you for answering.

Third party server. SIP. 

Do you need to convert the phone's firmware into SIP?  Do you have the necessary tools and firmware to achieve this?

What is the third-party call server?

I don't know if I have to convert it or not. I have looked at the user manual, but found nothing to help me. The server is sip.nsw.iinet.net.au

I don't know if I have to convert it or not.

Your phone would need to run SIP in order to join iiNet.  Unfortunately, you need to determine if the phone is indeed running SIP.  Can you power it up?

Ask the usual question: 

1.  Should the phone run NAT? 

2.  Does iiNet support ALG on the router? 

3.  Do you have a username & password ready?

Yes I can power it up. I actually have the IP address but when I put it into the computer

there is a lot of information but no where to enter the phone number, sip server etc.

Have a look at THIS.