My composition screen is all black.

If that's not it, please use the free MediaInfo and post a screenshot of the properties of your media in tree view:
https://mediaarea.net/en/MediaInfo

Many users are having issues with VFR. If the file is variable frame rate, use Handbrake to convert to constant frame rate before importing.
https://handbrake.fr/downloads.php

Shutter Encoder may also be used to convert to Constant Frame Rate:
https://www.shutterencoder.com/en/

If NVIDIA graphics, make sure to use a Studio Driver from NVIDIA (NOT the Game Driver), but not the latest version - it has issues with Premiere Pro and may have issues with After Effects.