I installed angular-cli and even then this command does not work, which can be or how I can add it.
It seems that you have to configure the environment variables, it should be the route
C:\Users\TuUsuario\AppData\Roaming\npm
And also
angular-cli\bin
Test once you have configured these variables restart your computer.
If you already have all this set up try to run
npm run ng serve
Edition
To configure your environment variables you must in the windows browser type Environment variables:
Path
npm
and your angular-cli
are generally found as follows: C:\Users\T015014\AppData\Roaming\npm\node_modules\angular-cli\bin;