Don't worry! This is very easy to do.
There are many different ways that you can go about it. Check out the video below to learn about all of the different methods and what they do. (Also make sure to download those extra freebies!)
- Use Blending Modes in your editing software to remove backgrounds. Use "Screen" or "Add" for black backgrounds, and "Multiply" for white backgrounds.
- To actually key out the background and create an Alpha Channel in your clip, use a plugin such as Demult (from HitFilm Ignite Express) or Unmult (from Red Giant Universe).
- After Effects has a preset called "Alpha From Lightness (Unmult)" that can be used to key a background. Using that preset does shift the colors of the stock footage slightly, so take caution when using it.
- Clips that don't have a perfectly black background require more advanced keying methods. To remove imperfections from your background, use the "Linear Color Key" effect in After Effects, or the "Hue & RGB Key" effect from HitFilm Ignite Express.