Trying to do a "clipping mask" a video to an image in After Effects I'm trying to do a clipping mask a video to an image in After Effects. Basically, I'm putting this video on top of an iPhone but track matte settings doesn't seem to be working for this. I saw Luma Inverted Matte setting works for what I'm trying to achieve but it leaves my video with like a white overlay on top (see screenshot). 



I've already searched the ends of Google for this but can't seem to solve the problem. All I'm really trying to achieve is post my XD prototype on Dribbble but to do so, I had to record my screen, import it to After Effects and now deal with the iPhone background. Please help!
Track mattes work by applying the alpha (transparency) or luma (≈ brightness) of one layer to the transparency of another layer. So in the case of an alpha matte, if the upper layer is transparent in an area (or opaque for alpha inverted), the lower layer will be too. In the case of luma mattes if the upper layer is black (or white for inverted*) then the lower layer will be transparent. The amount of transparency is controlled by the Luma of the matte layer. 

In your example To get fully transparent / opaque mattes use curves or levels or brightness and contrast effects to adjust the contrast of the upper layer. Or use whatever you used to create the image and output one with a transparent / black background.

 *could be the other way around, I always forget