Using Alpha Channel with mov transition

Motion Graphics
#1

Hi,

I downloaded a package of black and white brush transitions that are mov files.

I have one layer as the whole background, and then I want the brush transition in the corner of the screen revealing text.

I know its simple but how do I do that?

thanks!

#2

I would put the brush on a layer above and either alpha matte or alpha inverse the layer so that it acts as a mask and reveals the layer beneath