Updated Getting Started in README.md.

Author: ruofeidu

README.md

@@ -40,6 +40,41 @@ built upon
 or newer. We recommend using the `master` branch to build new projects with the
 AR Foundation SDK and refer to this branch when necessary.
 
+## Getting started
+
+These samples target
+[**Unity 2020.3.6f1**](https://unity3d.com/get-unity/download/archive) and
+require
+[**AR Foundation 4.2.0-pre.7**](https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@4.2/manual/index.html)
+or newer,
+[ARCore Extensions](https://developers.google.com/ar/develop/unity-arf) **1.24**
+or newer. Download `arcore-unity-extensions-1.24.0.tgz` from the ARCore
+Extensions for AR Foundation
+[releases page on GitHub](https://github.com/google-ar/arcore-unity-extensions/releases).
+
+Choose one of the following approaches to import the ARCore Extensions Package:
+
+1.  Manually update dependencies before launching the project:
+
+    *   Locate `arcore-depth-lab/Packages/manifest.json`.
+    *   Add the dependency of ARCore Extensions SDK with the loca path:
+        `"com.google.ar.core.arfoundation.extensions":
+        "file:{path/to}/arcore-unity-extensions-1.24.0.tgz",`
+    *   Launch the project with Unity Editor 2020.3.
+
+2.  Use Package Manager to import dependent package:
+
+    *   Use Unity 2020.3 to open the project.
+    *   It's expected that a window pops up and shows there are compile errors
+        in this project due to missing Extensions SDK, select **Continue**.
+    *   In Unity editor, navigate to `Window` -> `Package Manager`
+    *   Click the plus button, and choose the `Add package from tarball...`
+        option from the drop-down menu.
+    *   Locate `arcore-unity-extensions-1.24.0.tgz` and click Open.
+
+This project only builds with the Build Platform **Android**. Build the project
+to an Android device instead of using the **Play** button in the Unity editor.
+
 ## Sample features
 
 The sample scenes demonstrate three different ways to access depth. Supported
@@ -68,26 +103,6 @@ can be found in the `arcore_unity_sdk` branch.
     *   Environment relighting
     *   3D photo
 
-## Unity project setup
-
-These samples target
-[**Unity 2020.3.6f1**](https://unity3d.com/get-unity/download/archive) and
-require
-[**AR Foundation 4.2.0-pre.7**](https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@4.2/manual/index.html)
- or newer,
-[ARCore Extensions](https://developers.google.com/ar/develop/unity-arf) **1.24**
-or newer. Download `arcore-unity-extensions-1.24.0.tgz` from the ARCore
-Extensions for AR Foundation
-[releases page on GitHub](https://github.com/google-ar/arcore-unity-extensions/releases).
-Use Unity 2020.3 to open the project and import the package in `Window` ->
-`Package Manager`, click the plus button, and choose the `Add package from
-tarball...` option from the drop-down menu. Then locate
-`arcore-unity-extensions-1.24.0.tgz` and click Open.
-
-This project only builds with the Build Platform
-**Android**. Build the project to an Android device instead of using the
-**Play** button in the Unity editor.
-
 ## Building samples
 
 Individual scenes can be built and run by enabling a particular scene (e.g.,