here i can gave you the basic steps you need and i'll guide you to how accomplishing this proccess
By default most Cisco VoIP phones come configured for Call Manager, which uses the 'Skinny' protocol - SCCP.
most of other PBX has 2 implementations for this channel
• Skinny implements a very basic set of telephone functions and ships with asterisk.
• SCCP has implemented more of the SCCP protocol, so some class 5 features (hold, transfer, forward, etc) should work.
However, cisco phones can be reconfigured to use SIP (recommended for use with other PBX than CUCM):
make sure you have the next
- DHCP - By far the easiest way to configure the phones IP address is via DHCP, make sure you have a fully working DHCP server before continuing.
- TFTP Server - The phone picks its firmware and configuration up from a tftp server and you'll therefore need to have one on your LAN for this to work.
- Download Firmware , i know it is impossible for the normal users but may you can get from any integrator you know or from internet file sharing sites
- Create The Config Files . please check this link Asterisk
it is taking Asterisk as an example for free PBX