Transparency problems

Hi. I've just upgraded my photo morpher to the professional edition so that I could use the transparency options. Having done so, I still can't find a way to make the Flash files I create transparent.
The way I am attempting it is to load Gif files into the start and end pictures which have been saved with transparency (ie when I load them into my photo editing program, they do not have a white background - they have a transparent background). I then check the box in the timeline preferences to morph the alpha channel and set the counter to zero as suggested in the help files. However, when I render to SWF they still have a white background.
I presume there is a way of defining the alpha channel so that it is rendered as transparent but I haven't a clue how to do that. Can anyone help???
The way I am attempting it is to load Gif files into the start and end pictures which have been saved with transparency (ie when I load them into my photo editing program, they do not have a white background - they have a transparent background). I then check the box in the timeline preferences to morph the alpha channel and set the counter to zero as suggested in the help files. However, when I render to SWF they still have a white background.
I presume there is a way of defining the alpha channel so that it is rendered as transparent but I haven't a clue how to do that. Can anyone help???