Settings -> Extensions -> Add extension
Select Yes, this is a sidebar extension and Hosting Self-hosted (src), then paste
https://your-majesty.github.io/contentful-extension-linked-entries/build/
to Self-hosted URL
cd contentful-extension-linked-entries
# install dependencies
npm install
# login to contentful
npm run login
# select what space and enviroment you'll be using for development and deployment
npm run configure
# starts development server and publishes the extension in a development mode
npm run startcd contentful-extension-unlinks
# builds sources
npm run build