You need the permission of superuser levels to install React. In Linux/Unix the superuser account is generally named 'root'.
To get superuser privilege just run the following command on your terminal:
sudo -i
and then simply run the command to install React:
npm install -g create-react-app
However, the reactjs team encourages us to use the following command instead of installing a global package.
npx create-react-app app_name