Here are instructions to put the widget to use (you must know your device's Android version because there are some differences in the steps depending on it):
Versions up to Gingerbread (2.3.x)
1. Open the Home screen where you want to place the widget
2. Press Menu and touch Add, or just touch and hold and empty location on the Home screen
3. Choose Widgets in the menu
4. Find one of the two available sizes (3x2 or 4x3) in the widgets list
5. Adjust settings if you wish (press Back to exit)
Honeycomb versions (3.x)
1. Open the Home screen where you want to place the widget
2. Touch the + button at the top-right of the screen, or just touch and hold and empty location on the Home screen
3. Choose the Widgets tab
4. Find one of the two available sizes (3x2 or 4x3) in the widgets category
5. Drag the widget onto the Home screen where you want to add it
6. Adjust settings if you wish (press Back to exit)
Ice Cream Sandwich and later versions (4.x)
1. Open the Home screen where you want to place the widget
2. Touch the All apps icon
3. Choose the Widgets tab and swipe to the right to find one of the two available sizes (3x2 or 4x3)
4. Touch and hold the widget until the Home screen appears, slide it into place and lift your finger
5. Adjust settings if you wish (press Back to exit)
NOTE: If you use a Home screen replacement app such as Go Launcher or ADW Launcher, these steps may differ slightly.
1 Since version 1.3.0 the app runs normally after installed, but only to show brief instructions to help users, and also to overcome a quirk with Home screen widgets introduced with Honeycomb - they don't appear immediately in the list of installed widgets ↩