I tried running npm install -g angular-cli
I also tried adding it to the Enviorment Variables under PATH: (C:\\Users\\Administrator\\AppData\\Roaming\\npm\\node
This error is simply telling you that Angular CLI is either not installed or not added to the PATH. To solve this error, first, make sure you’re running Node 6.9 or higher. A lot of errors can be resolved by simply upgrading your Node to the latest stable version.
Open up the Terminal on macOS/Linux or Command Prompt on Windows and run the following command to find out the version of Node you are running: