Install yarn using npm

Use following to check whether yarn cli command is installed or not and also check its version

$ yarn --version
1.22.4

You can use npm to upgrade already installed yarn to the latest version or install it if it is not installed

$ npm install -g yarn                                                                             
/Users/<home-dir>/.nvm/versions/node/v12.11.1/bin/yarn -> /Users/<home-dir>/.nvm/versions/node/v12.11.1/lib/node_modules/yarn/bin/yarn.js
/Users/<home-dir>/.nvm/versions/node/v12.11.1/bin/yarnpkg -> /Users/<home-dir>/.nvm/versions/node/v12.11.1/lib/node_modules/yarn/bin/yarn.js
 yarn@1.22.4
 updated 1 package in 0.426s