First, you need the right plugins to export in the .nif and .kf formats. These are not yet available, although the ones for other games might be able to be jury-rigged to work.
Then you need to know what the game needs. Specifically things like the names of nodes, how many it has to have, how the keyframes are set up, what each animation has to be named, and so forth. As far as I know, this information has not been released.