This article shares some possible use cases for your app, as well as an example flow that could support each one. You're certainly not limited to these use cases, but they can be a helpful jumping-off point as you plan your app's implementation.
Your app can help the site owners upload media from a Pro Gallery to an external Social Media platform to increase their brand's popularity. You could retrieve the site's Pro Galleries, let the site owner select one, get the relevant media, and then upload the media items to the external platform.
Note: Make sure to include both the Wix media item IDs and the external media IDs in the mapping.
First, your app needs to create a mapping between the Wix media items and the external media. You can read about a possible way to do so in the Share a Pro Gallery on an External Platform example flow.
Note: Ignore the resulting webhook, so you don’t create an endless loop of updates.