If you are a git user, you can install the theme and keep up to date by cloning the repo:
git clone https://github.com/dracula/scrivener.git
Download using the GitHub .zip download option and unzip them.
- Extract master.zip
- Move Dracula.scrtheme to a safe location
- Open scrivener and import (Menu Items: Window> Themes> Load theme from file )
- Load Dracula.scrtheme and presto! Dracula!