Install and manage app extensions on iPhone
Some apps let you extend the functionality of your iPhone. An app extension may appear as a sharing option, an action option, a widget in Today View, a file provider, or a custom keyboard. For example, if you download Pinterest, Pinterest becomes another option for sharing when you click 
.
App extensions can also help you edit a photo or video in your Photos app. For example, you can download a photo-related app to apply filters to photos. See the Apple Support article How to edit with third-party apps and extensions in Photos.
Download and install app extensions
Download the app from the App Store.
Open the app, then follow the onscreen instructions.
Manage sharing or action options
Tap
, then tap More. (You may need to swipe the options left to reveal More.)Turn the sharing or action options on or off.
To reorder the options, touch and drag
.Tap Done.