If you try and upload a large image or video to Builder, you might get an error saying that the file is too large. In order to successfully upload the file you will need to make it smaller. Luckily, for videos you can use Handbrake to reduce the size of your file without losing quality. For images, an excellent tool is tinypng.
Alternatively, you can choose to use the embed block within builder to embed a YouTube or Vimeo video. You first will need to upload your video to one of those services, but it is a great option for long videos.