Follow this link: HTC Supersonic/ROMs - XDA-Developers
go down the page and find the link for Myns. Download that to you pc.
Do you know how to boot to recovery? Power the phone off. Hold down volume and power the phone back on. It will boot to a white screen(called hboot). use the volume keys to go to recovery and hit power to select. That will take you to recovery. use the volume keys to move to backup and perform a backup.