Question Help installing recovery! (TWRP)

Ok I've been flashing roms with the default htc recovery without a problem until now that requires me to switch over to TWRP to flash a pacman rom. I thought it would be a quick install with flashing a zip but TWRP doesn't do that for this device. Im trying to install this recovery but the latest version It says to install with the GOO MANAGER. I can't install that because they got rid of that app because of the new servers. I want to manually flash it with fastboot but I really don't know how to do that with the recovery.img. I've tried the TWRP app but that didnt do anything because it is too buggy. Can anyone help me?