Hi, Have you looked at the documentation?
http://docs.apigee.com/api-services/reference/saml-assertion-policy
If so, what is your particular question?
Please go through the below link as well
https://community.apigee.com/questions/23092/difference-between-soap-signing-using-x509-and-sam.html
Thanks and Regards,
Gaurav Bhandari