First, install the Validator using the adonis command:

adonis install @adonisjs/validtor

Create a resource route

adonis make:controller PostController --resource

Define the route in start/route.js

//..
Route.resource("posts", "PostController")
//..

Now, we can make a Validator for /posts/store

adonis make:validator StorePost

This will create a validator in /app/Validators.

Finally, To define a validator for a specific route in the definition, do something like this:

//..
Route.resource("posts", "PostController").validator([[["store", "StoreUser"]]])
//..

PSSS: I want this as short as it can while still answering question regarding the final code. 🥂