Add install guide to README

README.md

@@ -1,5 +1,25 @@
 # Echo
 
+## Installation
+
+### Release
+
+Go to [releases](https://github.com/echo-swent/echo/releases) and download the `app-debug.apk` asset from the latest release.
+
+### Artifact
+
+Go to the [Android APK Build](https://github.com/echo-swent/echo/actions/workflows/android.yml) workflow and download the `echo-app.apk` artifact from the latest successful run.
+
+## Authentication
+
+If you have trouble logging in, please use the following test credentials:
+
+- test@example.com
+- 123456
+
+> [!NOTE]
+> Make sure you are on the login page before entering the test credentials.
+
 ## Architecture
 
 ![Architecture](architecture.png)