You can edit your app’s Home Page design layout by:
1) Log into your App Manager and select your app.
2) Click Design from the left-hand-side of the screen (or the middle of the screen).
3) Scroll down to the Unified Home Page section and click the Change your homepage button.
The image you select must be 2732×2732 in size. The Unified Homepage settings includes a grid that enables you to easily see how your logo, etc will look in various orientations. We also provide a template that you can use. Click the Download template as PNG or PSD button to obtain the template.
Remember, you must republish your app in order for the changes to take effect in your live app.