Cannot register Cisco 6921 ip Phone to asterisk

Hii Guys I recently upgraded my (Skinny) IP phone to Sip but facing issues in registering the phone with Asterisk , I tried many XML config files given in online sources but I’m not able to get the right XML file which will help me! ( Note : I’m doing this with the help of TFTP server ) It would be of great help if you guys Help me to solve this …

Thanks In advance …