new docu

documentation/NgRx/NgRx.md

@@ -1,6 +1,7 @@
 [index.md](../index.md) > NgRx.md
 
 - [NgRx](#ngrx)
+- [Rough overview on how to use](#rough-overview-on-how-to-use)
 - [How the store works](#how-the-store-works)
   - [1. Create a state inside the reducer](#1-create-a-state-inside-the-reducer)
   - [2. Adding more reducers to the store service](#2-adding-more-reducers-to-the-store-service)
@@ -36,6 +37,47 @@ The reducers and effects inside the store service will be notified via the store
 
 The selector retrieves data from the state within the store service.
 
+# Rough overview on how to use
+
+```typescript
+export class UserComponent {
+  // A
+  store = inject(Store);
+
+  // B
+  user$ = this.store.select(selectUser);
+
+  onLogin(data: UserData): void {
+    // C
+    this.store.dispatch({
+      type: "[User] login",
+      user: data
+    });
+  }
+}
+```
+
+A) The store service is injected.
+
+B) Get data with `select()`. Pass a "selector". `selectUser` is a pure function and does nothing else than select a property from the store object.
+
+Imagine the store as an object:
+
+```typescript
+{
+  user: "Michael",
+  password: "1234"
+}
+```
+
+A selector to retrieve the username would then be something like this:
+
+```typescript
+selectUser = (state) => state.user
+```
+
+C) Change data with `dispatch()`. Pass an "action". Actions are events. An action is just a POJO (plain old javascript object), describes what is happening and holds data.
+
 # How the store works
 
 This example uses NgRx v7.