Here’s an example from AndroidManifest.xml. You need to specify the MAIN and LAUNCHER in the intent filter for the activity you want to start on launch
<application android:label="@string/app_name" android:icon="@drawable/icon">
<activity android:name="ExampleActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>