import android.app.Activity;
import android.os.Bundle;

public class AboutActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_about);

    }
}

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/about_text"
        android:id="@+id/about_content" />
</ScrollView>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.user.changeactivity" >

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="AboutActivity"
            android:label="@string/about_title">
        </activity>
    </application>
</manifest>

<resources>
 <!-- Base application theme. -->
  <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
   <!-- Customize your theme here. -->
  </style>
</resources>

public class AboutActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_about);

    }
}

public class AboutActivity extends Activity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_about);

        }
    }

<resources>
 <!-- Base application theme. -->
  <style name="AppTheme" parent="Theme.Holo.Light.DarkActionBar">
   <!-- Customize your theme here. -->
  </style>
</resources>