Hi
First of all you need a TFTP server, I would recommend Solarwinds from http://www.solarwinds.com ( its free )
Secondly, once you have installed Solarwinds you need to go to the "File" tab and then "Configure" and then "Security" and select "Send and Receive Files".
Solarwinds is now configured and ready to go, you need to place your SIPDefault.cnf , SIP(Mac).cnf and your SIP image in your TFTP root folder.
Now you need to make sure your DHCP server setting are correct, under "Scope Options" you need option 003 Router, 006 DNS Servers and 066 BootServer Host Name,
With all this setup power on your Cisco phone and hold down the "#" button until it says "Reset key sequence detected", then enter "1,2,3,4,5,6,7,8,9,star,0,hash" then press "2" and phone will say "Factory Reset Initiated". This forces the phone to get a new dhcp lease and therefore pick up all the above settings.
If all works okay the phone should optain all its network setting from the DHCP server and its SIP image and SIP setting from the TFTP server.
I hope this helps.