Get the app signature
Run the command keytool -list -v -keystore App Signature Path
using the keytool from the Android SDK
Retrieve the SHA1 value of the app signature, for example: SHA1: 0D:47:1A:3F:4C:21:C3:C2:26:8B:79:15:95:CF:F3:C5:D0:EE:E1:DE