Apple push notification certificate

The APN allows you to send push notification to your ios app users.

Login to your apple developer account.
Click on certificates, identifiers & profiles.
Go to keys screen. Click on + button to create new key.
You will be redirected to Register a new key screen.
Enter a key name (For example: If your app name is Quikapp you can enter the name as Quikapp APN certificate.)
Check the box next to Apple Push Notification services.
Click on configure next to sign in with apple.
Choose your app id from the dropdown.
Click on save.
Next, click on continue.
Select register to register a new key.
Download your key. (Note: The key can never be downloaded again after you download it once.)
Copy your key Id.
Next, upload this key to your Google firebase account.
Click setting icons in the left panel and select project settings.
Go to Cloud Messaging screen.
Click on upload below the APNs Authentication key section.
Select browse and upload the key file you downloaded from the apple store account.
Paste your key Id in the field.
To get your team Id, Go to membership in you apple developer account.
Copy your team Id.
Paste it in the team Id field.
Click on upload.