You are talking about basically 2 different plataforms.
you want to convert a frame png/bitmap character into shockwave flash object. then Flash player is the one you will be working into and will animate your char there.
Mugen is its own kind. when you are saying mugen.apk its no longer mugen, its just another fighting game that resembles mugen but it isnt. so you need to learn android programming language if a true apk you desire.