You can use the app Flashify to install the latest recovery once you've downloaded it to your phone. You can also put the recovery IMG file in your ADB/Fastboot folder and flash using the command "fastboot flash recovery nameofrecovery" (without quotation marks). Do this while connected via Fastboot USB mode while in the bootloader. There are also directions on the TWRP site how to install the recovery. If the recovery file is a ZIP file you can install it the same way you would a firmware update, by renaming the file 0P6BIMG and placing it on your external SD card, then rebooting to the bootloader. Select the Hboot option, allow the bootloader to scan for the ZIP file, then follow the on-screen instructions.