Please follow these steps to add an Art Gallery widget to your home screen:

1. Long press any blank space on your home screen to enter edit/jiggle mode.
2. Tap the plus button in the top of the screen.
3. Tap on 'Art Gallery' in the widget list.
4. Choose the size widget you want to add and choose 'Add Widget'.
5. Long press any blank space on your home screen to exit edit/jiggle mode.
6. Long press on the Art Gallery widget and choose 'Edit Widget'.
7. Choose which artwork you want to view and any other options like overlays you want to add.

With the free version of Widget Art Gallery, you can add one widget to your home screen. If you would like to add more, please upgrade to Art Gallery Premium. You can do this by tapping on 'Upgrade Art Gallery' in the Settings screen of the app.