Apply a theme to an Activity or application

Apply a theme to an Activity or application

To set a theme for all the activities of your application, open theAndroidManifest.xml file andedit the <application> tag to include theandroid:theme attribute with the style name. For example:

<application android:theme="@style/CustomTheme">

If you want a theme applied to just one Activity in your application, then add theandroid:theme attribute to the <activity> tag instead.

http://developer.android.com/guide/topics/ui/themes.html#ApplyATheme