Add a new activity to the AndroidManifest?

You put it inside of your application element, like this:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="your.package.name">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Activity1" android:label="@string/app_name"></activity>
        <activity android:name=".Activity2"></activity>
    </application>
    <uses-sdk android:minSdkVersion="4" />
</manifest>

Where .Activity2 is your second activity.