Update README.md

Author: IvanMurzak

README.md

@@ -15,7 +15,13 @@ Add the NotificationSender component to any object in a scene or prefab. Call th
 
 ![Codeless usage](https://imgur.com/kidklV8.png)
 
-# How to install
+# How to install - Option 1 (RECOMMENDED)
+- Install [ODIN Inspector](https://odininspector.com/)
+- [Install OpenUPM-CLI](https://github.com/openupm/openupm-cli#installation)
+- Open command line in Unity project folder
+- `openupm --registry https://registry.npmjs.org add extensions.unity.notifications`
+
+# How to install - Option 2
 - Install [ODIN Inspector](https://odininspector.com/)
 - Add this code to <code>/Packages/manifest.json</code>
 ```json