To save it as an fc2 file, open the libraries 'Expressions' palette, browse to the part of the library that you want to save it to, click the "+" symbol at the bottom of the palette. This saves the parameter value for the head morphs. In order for the fc2 file to work correctly on a figure, you need to have the same morphs present in the head as when the fc2 file was saved.

As an alternative to the above, you can use SceneFixer to save a delta injection pose. Such a pose will embed the morph deltas in the pose file, and thus it can apply the face morph even when no other morphs have not been injected into the figure.