This theme is based on the Streamlabs OBS. It uses the Rachni theme included with OBS as a base. I definitely recommend installing Noto Sans if you do not already have it.
Unzip the file
Copy the contents to your OBS installation ...\obs-studio\data\obs-studio\themes (Default: C:\Program Files (x86)\obs-studio\data\obs-studio\themes)
Launch OBS and select the Streamlabs theme in Settings > General > Theme