Yes, you will need to communicate this information to the identity provider.
For example, you could email the SAML metadata to the identity provider or make it available through a download link.
One way to create the SAML metadata is to run the CreateMetadata project under the Examples\Metadata folder.
The SAML metadata will include the assertion consumer service (ACS) URL.
Our SAML Metadata Guide
includes more information on creating metadata.