Node.js is already installed on your server


Node.js is already installed on your server. You can check the version by entering "node -v" into Terminal without quotations.



Use NVM to change the version of Node and NPM


If you wish to use a different version of Node.js, we recommend using nvm to manage Node and npm's versions. You can use this to adjust it to the version you currently need.


Sources:

Node.js Documentation