(use-package one-midnight :straight (:type git :host github :repo "one-midnight-theme/one-midnight.el"))
First, clone this repo:
$ git clone https://github.com/jonathanchu/one-midnight.el.git
Then, add this to your Emacs config:
(add-to-list 'custom-theme-load-path "~/.emacs.d/path/to/one-midnight.el/")
To load this theme on Emacs startup and make it the default, add this to your Emacs config:
(load-theme 'one-midnight t)