Can I add my app to the sharing popup menu? (Like Facebook, Twitter and other apps) I would like to share image from iPhone photo library to my app. If yes could someone please leave me some starting point (documentation link). I couldn't find it anywhere.
Can I add my app to the sharing popup menu?
YES.
You may need to add a Share Extension to your app.
You can find some articles searching with "ios swift share extension".
If you find some difficulty implementing your own Share Extension, many readers of this site can help if you can provide some more concrete details of your issue.
(This old article of Apple may also be useful: App Extension Programming Guide.)