Look here at post #28 and #30. http://forum.xda-developers.com/show...2717928&page=3 . Download that .zip template
I think you can put the TWRP recovery.img (it has to be renamed to recovery.img) inside the zip as directed, put it on the SD card and let the bootloader automatically detaect and flash it. Once its completed you would have to power down and remove it from the SD card otherwise it would try to update again next time you go into the bootloader. That should load a recovery from which you can flash a ROM.