yarn link

// yarn link (in package you want to link)

$ cd ../react-relay
$ yarn link react

// you'll see a success message
success Registered "react"

// go to your project folder and link package -> yarn link [package-name]
yarn link vx.x.x

// you will see a success message letting you know your package is linked
success Using linked package for "react"

// run yarn to apply package to your project
yarn