I never did this myself, but I would just follow the description here
https://developer.spotify.com/documentation/android/tutorials/application-fingerprints
So if you use a Windows PC, open a Powershell window and type
keytool -alias androiddebugkey -keystore yourKeystoreFile -list -v | grep SHA1
More about keytool see here Search results for 'Keytool' - MIT App Inventor Community
See also Error al compilar mi aplicación! Keystore Personalizado! - #3 by Boban
Taifun