Update New-AzADAppCredential.md (Azure#20317)

Clarify examples. Also fixes the "Unable to get certificate thumbprint" issue in the portal, by giving an example of passing $CertificateThumbprint variable to the -CustomKeyIdentifier parameter.

Co-authored-by: NanxiangLiu <[email protected]>

Author: robinmalik

src/Resources/Resources/help/New-AzADAppCredential.md

@@ -122,28 +122,30 @@ Creates key credentials or password credentials for an application.
 
 ## EXAMPLES
 
-### Example 1: Create key credentials for application
+### Example 1: Create key credentials for an application
+
 ```powershell
-# ObjectId is the string representation of a GUID for directory object, application, in Azure AD.
-$Id = "00000000-0000-0000-0000-000000000000"
-# $cert is Base64 encoded content of certificate
-$credential = New-Object -TypeName "Microsoft.Azure.PowerShell.Cmdlets.Resources.MSGraph.Models.ApiV10.MicrosoftGraphKeyCredential" `
-                                 -Property @{'Key' = $cert;
-                                 'Usage'       = 'Verify';
-                                 'Type'        = 'AsymmetricX509Cert'
-                                 }
-New-AzADAppCredential -ObjectId $Id -KeyCredentials $credential
+# $ObjectId should be the the 'Object ID' GUID associated with the Azure app registration.
+# $CertificateThumbprint should be the thumbprint of the certificate.
+# $Cert is the base64 encoded content of the certificate.
+$ObjectId = "00000000-0000-0000-0000-000000000000"
+$Credential = New-Object -TypeName `
+  "Microsoft.Azure.PowerShell.Cmdlets.Resources.MSGraph.Models.ApiV10.MicrosoftGraphKeyCredential" `
+  -Property @{'Key' = $Cert;
+  'Usage'       = 'Verify';
+  'Type'        = 'AsymmetricX509Cert'
+}
+New-AzADAppCredential -ObjectId $ObjectId -KeyCredentials $Credential -CustomKeyIdentifier $CertificateThumbprint
 ```
 
-Create key credentials for application with object Id $Id
+### Example 2: Create password credentials for an application
 
-### Example 2: Create password credentials for application
 ```powershell
-# ApplicationId is AppId of Application object which is different from directory id in Azure AD.
-Get-AzADApplication -ApplicationId $appId | New-AzADAppCredential -StartDate $startDate -EndDate $endDate
+# $ApplicationId` should be the the 'Application ID' GUID associated with the Azure app registration.
+$ApplicationId = "00000000-0000-0000-0000-000000000000"
+Get-AzADApplication -ApplicationId $ApplicationId | New-AzADAppCredential -StartDate $startDate -EndDate $endDate
 ```
 
-Create password credentials for application
 
 ## PARAMETERS