Added PS variables

Added PS variables and committed suggested changes

samples/Management/PowerShell/AddingSchematoSchemagroups/Addingschematoschemagroup.ps1

@@ -7,11 +7,12 @@ $Fields = @{
     client_secret = "<Application_Secret>"
   };
 
-  
+  #update tenant ID to the correct tenant where you would like to get authorization token from
   $response = Invoke-RestMethod –Uri "https://login.microsoftonline.com/<Tenant_ID>/oauth2/token" –ContentType "application/x-www-form-urlencoded" –Method POST –Body $Fields
-
+   
   #response would have bearer token in the properties that we would use to trigger next call.
-
+  $token = $response.access_token
+ 
   #Step 2- You can declare schema JSON associated to schema in $Body variable below
   $Body = @"
   {
@@ -32,13 +33,19 @@ $Fields = @{
 "@ 
 
 #Step 3- This Uri needs to have details added- namespace name, schema group name and schema name respectively.
-$uri = 'https://<Namespace_Name>.servicebus.windows.net/$schemagroups/<SchemaGroup_Name>/schemas/<Schema_Name>?api-version=2020-09-01-preview'
+
+$NamespaceName      = '<namespacename>'
+$SchemaGroupName    = '<schemagroupname>'
+$SchemaName         = '<SchemaName>'
+
+
+$uri = "https://$NamespaceName.servicebus.windows.net/$schemagroups/$SchemaGroupName/schemas/$SchemaName`?api-version=2020-09-01-preview"
 
 #Step 4- These headers would be sent along with the API Call
 $headers = @{
     "Content-Type" = "application/atom+xml;type=entry;charset=utf-8"
     "Serialization-Type" = "Avro"
-    "Authorization" = "Bearer " + $response.access_token
+    "Authorization" = "Bearer " + $token
 }
 
 #Step 5- This step shows the final call that we make to add schema under the schema groups,