Production - Video Overlay

In shows such as Say Yes to the Dress confetti like overlays are used as shown below:



I was curious on how I could do this in iMovie so went on Youtube to research if I was able to do it.

I found a website called KeepVid which allows you to download videos to import into iMovie. I found an overlay video I liked which showed heart shaped cherry blossom which looked like confetti. I felt this would work well as the pink colour contrasted well over the white dresses and the hearts are very symbolic of love, marriage and what the wedding dresses represent. I wanted to use this effect in my introduction for my documentary as I want to follow the codes and conventions set in the genre. There is a link to this video here.
I was not sure if I would be able to use the video due to copyright issues however in the video bio it specifies that the video is not copyrighted and free for anyone to use.

I put the link of the video - (https://www.youtube.com/watch?v=fNpcFiWa_4k) into the download bar  which it then downloaded onto my desktop.



I then imported the video into iMovie by dragging and dropping it over my current footage. However, I realised that the video was black and that the overlay would not show my other footage. I thought I would be unable to make the video how I wanted by discovered I could change the opacity.






I turned the opacity down slightly which removed the black background and revealed my wedding dress footage.
This was the outcome of the effect:



Video Overlay Example from Ella on Vimeo.