Update README.md

README.md

@@ -7,5 +7,69 @@ FaceDetector is:
 - detects faces
 - works on Android
 - very simple to use
-- comes with (Fotoapparat)[https://github.com/Fotoapparat/Fotoapparat] integration (but you can use it with whatever you like)
+- comes with (https://github.com/Fotoapparat/Fotoapparat)[Fotoapparat] integration (but you can use it with whatever you like)
 - with a C++ core which can easily be ported to iOS (we have plans for that)
+
+## How it works
+
+For simplicity let's assume that you are using Fotoapparat as your camera library. If you don't - plese refer to `FaceDetector` documentation (it is just 1 method).
+
+### Step One
+
+If you would like to display detected faces right on top of camera, set up your layout as following (otherwise skip this step).
+
+```xml
+<io.fotoapparat.facedetector.view.CameraOverlayLayout
+        android:layout_width="match_parent"
+        android:layout_height="match_parent">
+
+    <!-- Adjust parameters as you like. But cameraView has to be inside CameraOverlayLayout -->
+    <io.fotoapparat.view.CameraView
+        android:id="@+id/cameraView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+    <!-- This view will display detected faces -->
+    <io.fotoapparat.facedetector.view.RectanglesView
+        android:id="@+id/rectanglesView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:rectanglesColor="@color/colorAccent"
+        app:rectanglesStrokeWidth="2dp"/>
+
+</io.fotoapparat.facedetector.view.CameraOverlayLayout>
+```
+
+### Step Two
+
+Create `FaceDetectorProcessor`:
+
+```java
+FaceDetectorProcessor processor = FaceDetectorProcessor.with(this)
+    .listener(faces -> {
+        rectanglesView.setRectangles(faces);  // (Optional) Show detected faces on the view.
+
+        // ... or do whatever you want with the result
+    })
+    .build()
+```
+
+### Step Three
+
+Attach it as processor to `Fotoapparat`
+
+```java
+Fotoapparat.with(this)
+    .frameProcessor(processor)
+    // the rest of configuration
+```
+
+And you are good to go!
+
+## Set up
+
+Add dependency to your `build.grade`
+
+```groovy
+
+```