NPM not recognized

How to fix?
npm : The term 'npm' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the
spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ npm install -g @angular/cli
+ ~~~
+ CategoryInfo : ObjectNotFound: (npm:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException