ANDROID_HOME with the address of the SDK folder.
To set ANDROID_HOME permanently follow the below steps
1. Right click on My Computer > Properties > Advanced System Settings > Environment variables
2. Add system variable
name = "ANDROID_HOME"
value = "E:\Users\user\AppData\Local\Android\sdk"
(Enter your android sdk path here)
3. Above system varialbe you can see your PATH, Edit PATH
"%PATH%;%ANDROID_HOME%\tools;%ANDROID_HOME%\platform-tools"
4. click OK and done configuration!
reference:
https://www.360logica.com/blog/how-to-set-path-environmental-variable-for-sdk-in-windows/