Since the packages are stored into Github Packages, you have to follow a few more steps to make it work.

1. In a command line, type

npm login --registry=https://npm.pkg.github.com/ --scope=@derniercri

2. Add a .npmrc file to your project, that contains

   @derniercri:registry=https://npm.pkg.github.com

3. Install the desired package

yarn add @derniercri/YOUR_PACKAGE

Instead of using project's .npmrc file, you can edit your ~/.npmrc and add/edit these lines :

//npm.pkg.github.com/:_authToken=YOUR_TOKEN
@derniercri:registry=https://npm.pkg.github.com

If you want to release a new version, just run

yarn release

It will prompt you with several questions and at the end, it will push a new version to Github.