Update README.md

Author: af-margot

README.md

@@ -31,13 +31,39 @@
 
 ## <a id="add-sdk-to-project"> 📲 Adding the SDK to your project
 
+**Using unitypackage:**
 1. Clone / download this repository.
 2. [Import](https://docs.unity3d.com/Manual/AssetPackages.html) the appsflyer-unity-plugin-*.unitypackage into your Unity project.
 3. Go to Assets >> Import Package >> Custom Package.
 4. Select the appsflyer-unity-plugin-*.unitypackage file.
 
 > **Note:** The plugin uses the [The External Dependency Manager for Unity](https://github.com/googlesamples/unity-jar-resolver) (EDM4U) (formerly Play Services Resolver / Jar Resolver). If you do not want to use EDM4U see the [Installation guide](/docs/Installation.md) for more details.
 
+**Using Unity Package Manager:**
+1. Go to your packages folder, and open `manifest.json` 
+2. Add Google game package registery fpr the external dependency Manager. 
+```
+  "scopedRegistries": [
+    {
+      "name": "Game Package Registry by Google",
+      "url": "https://unityregistry-pa.googleapis.com",
+      "scopes": [
+        "com.google"
+      ]
+    }
+  ]
+```
+
+4. Add appsflyer-unity-plugin in the dependency :
+Add this line for the regular mode
+```
+ "appsflyer-unity-plugin": "https://github.com/AppsFlyerSDK/appsflyer-unity-plugin.git#upm"
+```
+ Or this line for Strict mode :
+```
+ "appsflyer-unity-plugin": "https://github.com/AppsFlyerSDK/appsflyer-unity-plugin.git#Strict-upm"
+```
+
 
 ## <a id="init-sdk"> 🚀 Initializing the SDK