In you AndroidManifest.xml you can specify the screen-sizes your app supports, by using the supports-screens element.
Here is an example:

<supports-screens
android:smallScreens="true"
android:normalScreens="true"
android:largeScreens="true"
android:xlargeScreens="true"
>

In your AVD (Android Visual Device) Manager, you have defined the visual device(s) for your Android Emulator. Here the “Skin” attribute defines the screen-size, you can select between: QVGA, WQVGA*, HVGA, WVGA* and WXGA.

To help you test the supported screen-sizes for you app, here is the mapping between the supports-screens element and the Emulator Skins attributes:

• smallScreens = QVGA
• normalScreens = WQVGA*/HVGA/WVGA* (depending on density)
• largeScreens = WVGA*
• xlargeScreens = WXGA

Read more about the supports-screens element in the Android Developer Guide.