configuring saml-sample (SP) to work with Okta (IdP)

Some details:
Okta (acting as the IDP) supports 2 methods of authentication:
In IDP initiated the flow is:
User goes to Okta and from their framework gets to the SP.
In SP initiated the flow is:
User goes to the target SP first. SP redirects the user to the configured Login URL ( Okta’s generated app instance url) sending the SAMLRequest. Okta handles the SAML request, generates the SAML response, and the SP receives the SAMLResponse and verifies that it is correct.

When I configure my SP (spring-saml-sample) in the Okta system, I need to supply some data on my SP, such as "post back URL", "recipient" and "audience restriction".
Can someone help me and explain to me what these fields are and what are the correct values that are relevant to spring-saml-sample? where I take the values from?

thanks
ohad