Refactor image file name in tutorial documentation

docs/en/tutorials/modular-crm/part-02.md

@@ -41,7 +41,7 @@ We will use the *DDD Module* template for the Product module and the *Empty Modu
 
 Right-click the `modules` folder on the *Solution Explorer* panel, and select the *Add* -> *New Module* -> *DDD Module* command:
 
-![abp-studio-add-new-dd-module](images/abp-studio-add-new-dd-module.png)
+![abp-studio-add-new-ddd-module](images/abp-studio-add-new-ddd-module.png)
 
 This command opens a new dialog to define the properties of the new module. You can use the following values to create a new module named `ModularCrm.Products`:
 

docs/en/tutorials/modular-crm/part-05.md

@@ -254,6 +254,12 @@ Click the *Ok* button. Now you can check the *Packages* under the `ModularCrm.Or
 
 ![abp-studio-added-ddd-contracts-package](images/abp-studio-added-ddd-contracts-package.png)
 
+Return to your IDE, open the `ModularCrm.Ordering` module's .NET solution and create an `IOrderAppService` interface under the `Services` folder for `ModularCrm.Ordering.Contracts` project:
+
+````csharp
+//Checkpoint
+````
+
 ## Creating the User Interface
 
 Since this is a non-layered module, we can use entities and repositories directly on the user interface. If you think that is not a good practice, then use the layered module template as we've already done for the *Products* module. But for the Ordering module, we will keep it very simple for this tutorial to show it is also possible.