Animation re-sizing

Hey guys, got what is probably a pretty dumb question. When i import animation frames (from a program such as spriter or MS paint) each frame is a different size so I have to resize them in the external stencyl editor (pencyl). This is pretty difficult and tedious. Is there an easier way to do this?

Are they all the same size when you make the file? I would make sure they are all the same when you first make them.