Click username > Switch to Lightning Experience.
Click Gear and select Setup Home.
Navigate to Identity > Single Sign-On Settings.
Click the created configuration (not for Edit).
Click Download Metadata.
Open the Advanced Authentication Administration portal.
Click Events > Add to add a new event.
Create an event with the following parameters.
Name: Salesforce
Chains: select the required chains.
Click Browse to Upload SP SAML 2.0 metadata file. Open the Salesforce metadata file and click Save.