Ask Yammer's customer support to enable SAML 2.0 Single Sign-On for your account. They'll ask for the following information:
External key:
Sign in to the Okta Admin app to have this variable generated for you.Redirect Login URL
Sign in to the Okta Admin app to have this variable generated for you.Public certificate
Sign in to the Okta Admin app to have this variable generated for youMetadata
Sign in to the Okta Admin app to have this variable generated for you.
Wait for Yammer to send you further instructions on how to enable Single Sign-On for your organization. If you want to allow your users to sign-on to Yammer immediately, you can change the sign-on mode to Secure Web Authentication.
You can assign Yammer access to your users at anytime from their user profile. Go to the People page within Okta to view and edit user profiles.