How to obtain the Server key for iOS configuration ?

Step 1 : Go to Firebase and Sign in to your account.
Step 2 : Click on Get Started
Step 3 : Click on Create a Project
Step 5 : Access your project settings, and locate the "Cloud Messaging API" section.

Step 6 : Click on the three dots and select "Manage API in Google Cloud Console."

Step 7 : Proceed to click the "Enable" button.

Step 8 :  After enabling, refresh the Firebase page, and copy the server ID from the Cloud Messaging API section.