Added documentation for Install application from APK

docs/Installing-an-application-from-APK.md

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+# Installing an application from APK
+
+## Introduction
+
+This guide will show you how to install an application from an APK file on your Android emulator.
+
+## Prerequisites
+
+- Setup Android Emulator using [mobile-helper-tool](https://github.com/nightwatchjs/mobile-helper-tool)
+- APK file of the application you want to install
+- `adb` command should be available in your terminal. You can check this by running `adb --version` in your terminal.
+
+## Assumptions
+- APK path is `/path/to/your/app.apk`
+- Application package name is `your.app.package`
+
+## Steps
+
+### Check if Emulator is running
+```bash
+adb devices
+```
+
+### Install the application
+```bash
+adb install /path/to/your/app.apk
+```
+
+### Verify the installation
+```bash
+adb shell pm list packages -f | grep your.app.package
+```
+
+### Remove the application
+```bash
+adb uninstall your.app.package
+```