Hi Freddie,
You may check the following links
https://supportforums.cisco.com/discussion/10998266/sepcnfxml-file-needed-3rd-party-pbx
http://www.888voip.com/configuring-cisco-7975-ip-phones-for-sip/
https://www.voip-info.org/wiki/view/Asterisk+phone+cisco+79x1+xml+configuration+files+for+SIP
HTH
Manish