Default doubleTwist... help?

Gosh, I really didn't want to ask but I gave up after googling for hours on how to get m4v (or wmv, mp4 files) into my Xoom via doubleTwist usb sync. I was able to get songs to appear there but not videos.

SO... help?

P.S. first time using doubleTwist.
m4v is a must have to work on Xoom because most videos' format is m4v that has menus.

Thanks, Kat