Complete the FluentValidation Integration document.

docs/en/FluentValidation.md

@@ -1,3 +1,54 @@
 # FluentValidation Integration
 
-TODO
+ABP Validation infrastructure is extensible. [Volo.Abp.FluentValidation](https://www.nuget.org/packages/Volo.Abp.FluentValidation) NuGet package extends the validation system to work with the [FluentValidation](https://fluentvalidation.net/) library.
+
+## Installation
+
+It is suggested to use the [ABP CLI](CLI.md) to install this package.
+
+### Using the ABP CLI
+
+Open a command line window in the folder of the project you want to install the Volo.Abp.FluentValidation NuGet package and type the following command:
+
+````bash
+abp add-package Volo.Abp.FluentValidation
+````
+
+### Manual Installation
+
+If you want to manually install;
+
+1. Add the [Volo.Abp.FluentValidation](https://www.nuget.org/packages/Volo.Abp.FluentValidation) NuGet package to your project:
+
+   ````
+   Install-Package Volo.Abp.FluentValidation
+   ````
+
+2.  Add the `AbpFluentValidationModule` to the dependency list of your module:
+
+````csharp
+[DependsOn(
+    //...other dependencies
+    typeof(AbpFluentValidationModule) //Add the FluentValidation module
+    )]
+public class YourModule : AbpModule
+{
+}
+````
+
+## Using the FluentValidation
+
+Follow [the FluentValidation documentation](https://fluentvalidation.net/) to create validator classes.  Example:
+
+````csharp
+public class CreateUpdateBookDtoValidator : AbstractValidator<CreateUpdateBookDto>
+{
+    public CreateUpdateBookDtoValidator()
+    {
+        RuleFor(x => x.Name).Length(3, 10);
+        RuleFor(x => x.Price).ExclusiveBetween(0.0f, 999.0f);
+    }
+}
+````
+
+ABP will automatically find this class and associate with the `CreateUpdateBookDto` on object validation.