To play back a storyboard file, use M.U.G.E.N's -storyboard command-line option. The syntax is:

mugen -storyboard <storyboard filename>
For example, to play back data/kfm/intro.def, you would type:

mugen -storyboard data/kfm/intro.def
The storyboard search directory defaults to data/, so you can omit the "data/" part if you like. The following will also play back data/kfm/intro.def:

mugen -storyboard kfm/intro.def
This feature can be useful for quickly testing your storyboards as you build them.