Update README.md (#553)

Add information on how to download / install

README.md

@@ -9,6 +9,22 @@ The InvenTree mobile / tablet application is a companion app for the [InvenTree
 
 Written in the [Flutter](https://flutter.dev/) environment, the app provides native support for Android and iOS devices.
 
+## Installation
+
+You can install the app via the following channels:
+
+### Google Play Store (Android)
+
+Download and install from the [Google Play Store](https://play.google.com/store/apps/details?id=inventree.inventree_app&hl=en_AU)
+
+### Apple Store (iOS)
+
+Download and install from the [Apple App Store](https://apps.apple.com/au/app/inventree/id1581731101)
+
+### Direct Download (Android)
+
+We provide direct downloads for Android users - view our [download page via polar.sh](https://polar.sh/inventree/products/299bf0d5-af88-4e0f-becf-c007ad37ecf2)
+
 ## User Documentation
 
 User documentation for the InvenTree mobile app can be found [within the InvenTree documentation](https://inventree.readthedocs.io/en/latest/app/app/).