Set up "Sign with Apple"

Inputs you will need from our development team
Domains and Subdomains	You will get this from us
Return URLs	You will get this from us
Outputs you will get from this guide and you should sent us
Identifier	Send us this info
Team ID	Send us this info
Key ID	Send us this info
.p8 Key file	Send us this file

1. Enable “Sign in with Apple” for specific App ID

Login to Apple developer
Go to Identifiers https://developer.apple.com/account/resources/identifiers/list
Find and select your existing app identifier to edit existing configuration (if you use both STG and PROD apps, set this for both apps)
In “Capabilities” list find “Sign in with Apple” and enable it
Select “Enable as primary App ID” and click “Save”
Confirm changes with “Save” also on “Edit your App ID Configuration” form

Go to Keys https://developer.apple.com/account/resources/authkeys/list
Add new key and name it “Sign in with Apple” and select option “Sign in with Apple”
Besides “Sign in with Apple” option above select “Configure” and then select App ID and click “Save”
You will be redirected back to the Key setup, where you should click “Continue”
Then select “Register”
Now click “Download” button to download the .p8 file and copy your “Key ID”. Send this file and Key ID to us.

Save your downloaded file somewhere where you can find it as it can only be downloaded once!

Go to Identifiers
Add new Identifier and choose “Services ID”
Set “Description” as “Sign in with Apple” and set the “Identifier” field to custom value, best in reverse-domain name style string, for example: “com.CompanyDomain.MyAppName”, then click “Save” and “Register”
By click on newly created Service ID, you can edit it and enable “Sign in with Apple” option
Select “Configure” button besides “Sign in with Apple” to set the configuration.
Set Primary App ID
Now add new “Website URLs” by clicking on “+“ button and paste into “Domains and Subdomains” and “Return URLs” fields the data our team have sent you. Then click “Next”
If you correctly added them you can see them in dropdown. You cannot select them. Now click “Done”
On the following page click “Save” and that’s it.