You can also find this custom rule under the appendix section ADFS Custom Rule
The federation endpoint will be the URL of your ADFS server combined with the relative address of
Take note of the blue message that appears. Providers are loaded in when Identity Server starts up, so you must restart the application in IIS before your provider will be usable.
Open the AD FS Management tool.
Verify that the Source user ID claim is available by going to ADFS > Service > Claim Descriptions.
Check the list for a claim with the name ‘Source user ID’ as defined in the appendix of this document under ADFS Claim Descriptions.
If the Claim Description does not exist, then add it.
Add a new Relaying Party Trust by going to AD FS > Trust Relationships > Right click on Relying Party Trusts and select ‘Add Relying Party Trust’.
Select ‘Start’ to begin.
Select ‘Enter data about this relying party manually’ and select ‘Next’.
Enter ‘Identity Server’ for the name (or a name of your choosing) and select ‘Next’.
Leave the default ‘AD FS profile’ selected and select ‘Next’.
Select ‘Enable support for WS-Federation Passive protocol’ and then enter the ‘Relying Party WS-Federation Passive Protocol URL’ value recorded during the creation of the Identity Server provider (You can go back to Identity Server to get the value).
Ensure that ‘Open the Edit Claim Rules dialog for this relying party trust when the wizard closes’ checkbox is selected.
Select ‘Add Rule…’.
Select ‘Send Claims Using a Custom Rule’.
Enter ‘Identity Server Rules’ for the ‘Claim rule name” or a name of your choosing.
Enter the custom rule defined in the appendix under ADFS Custom Rule.
Select ‘Finish’ and then select ‘OK’.