It sounds like you're looking to do a technique known as "masking". At this time, Edge Animate does not have masking functionality, but it is something that is being looked into for a future release. : )
However, there are techniques that users have developed that provide a work around to achieve the effect you are looking for. Check out this thread below to see how to do the technique:
At the bottom, the user aa_lique describes taking rectangles that are the same color as the background color and animating them to uncover the image behind them. I have also authored a tutorial that utilizes a similar technique to uncover a logo in a radial "wipe" looking effect:
I hope this helps! Let me know if you need further clarification! If you'd like, I can make a sample project for you to show you how to do the masking workaround technique.
Could you show the sketch or something similar?