You can upload media files from your local computer for your application's use. The App SDK uses the images in these media files as icons and as button labels. Some images are specific to icons and buttons in a particular view and some, like the label for the cancel button, are defined and used throughout your application.
Media files are always platform-specific, so you must select a platform before you can upload a media file. All of the images for a given platform must be in a single ZIP file, but that ZIP file can have a directory structure of your choosing.
Click the Upload button under Media Files.
Select the ZIP file that contains your images.
Click the Open button to import the file into your tenant.