Edit:
If the below steps do not work for you, check this answer as nodemon might not be added to the PATH after installation.
Nodemon is a Node Package that is managed by the Node Package Manager (NPM).
To install Node Packages, you need to use the following command,
npm i package-name // This will install the package locally as a dependency
npm i -D package-name // This will install the package locally as a dev dependency
npm i -g package-name // This will install the package globally
And so, to install nodemon globally, you would do,
npm i -g nodemon // For Windows or if you installed NodeJS using NVM on linux
sudo npm i -g nodemon // If you installed NodeJS from from apt or other linux package manager.
node install whatever
is not a command and obviously won't work.
sudo npm install -g nodemon
:D – Jervz09