Added comment to advice enabling PayPal feature.

Author: xianwang423

AuthorizeNETtest/Api/Controllers/SampleTest/CreateTransactionSampleTest.cs

@@ -270,6 +270,10 @@ public void SampleCodeCreateTransactionWithApplePay()
         [Test]
         public void SampleCodeCreateTransactionWithPayPal()
         {
+            /*
+             * Please enable the PayPal feature of your ANet merchant account.
+             */ 
+
             //Common code to set for all requests
             ApiOperationBase<ANetApiRequest, ANetApiResponse>.MerchantAuthentication = CustomMerchantAuthenticationType;
             ApiOperationBase<ANetApiRequest, ANetApiResponse>.RunEnvironment = AuthorizeNet.Environment.SANDBOX; //TestEnvironment;