2 ways:
- Download a TWRP flashable .zip. While in recovery, wipe cache. Then flash .zip. Then go to "advanced options" in CWM and choose "reboot recovery"
- Download a TWRP recovery.img, and flash it through fastboot. Make sure you have fastboot and adb drivers. Connect phone to pc in fastboot mode. Open a CMD window from where you have your adb and fastboot files, as well as the recovery.img file. In the cmd window type "fastboot flash recovery _______.img" Where the blank spot is, is where you would put the name of your recovery .img file.