Android : keytool is not recognized as an internal or external command

I wish to genrate application signature for my app which will later be integrated with facebook.

In a facebook's tutorial I found this command

keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore | "C:\Users\abc\openssl\bin\openssl.exe" sha1 -binary | "C:\Users\abc\openssl\bin\openssl.exe" base64

and It is written over there that by running this on cmd my process of generating the signature will start

this command gives an error :

keytool is not recognized as an internal or external command.