Unhappy putting omnirom on motorola xoom help

I am desperately trying to figure this out. I have rooted my xoom. So now, I am in process of using BigPart to partition and install omnirom. I have found the instructions on here, which seem forward and simple. I boot into recovery mode like it says. I put the TWRP BigPart and omni-4.4.2-201XXXXX-wingray-HOMEMADE_XXXX.zip on my sdcard (because I am assuming they don't mean internal memory).

Well, when in revover mode I want to flash TWRP BigPart but I can not find it in the recovery options so I am also assuming I cant find my sdcard cause every thing I go to in recovery mode only leads me to files on my internal memory.

I would be most greatful for any help