Ultimate Fields is a plugin, that allows you to add custom fields in many places throughout the WordPress administration area, supporting a total of more than 30 field types, including repeaters, layouts and etc.
Ultimate Fields is available in the WordPress.org plugins repository, which means that you can install it as a standard plugin through the dashboard.
Please read the As a Composer package section of the documentation.
If you'd like to contribute back to the plugin, you can clone this repository as a plugin, but you will need to manually compile the stylesheets, which is done through NPM:
cd /PATH-TO-YOUR-WEBSITE/wp-content/plugins
git clone git@github.com:RadoslavGeorgiev/ultimate-fields.git
cd ultimate-fields
npm install
npm run buildOnce you do so, the plugin will be fully compiled and ready to use. During development you might want to execute npm run watch in order for your changes to be applied immediately.