Configuring the Security Fabric with SAML:
Log in to the root FortiGate.
Go to Security Fabric > Fabric Connectors and double-click the Security Fabric Setup card.
In the Topology tree, hover over a FortiGate and click Configure.
Click Ok in the configure window
Once installed the Certificate needs to be exported
Export it as a Base-64 encoded X.509 (.CER)
You will also need to download the IdP Certificate
Upload the exported CER file.