You can not add option menually, it will display automatically according to share content, for example, if share content is only text then not show "iCloud photo sharing" But share content has the image then automatically show option accordingly.
If you want to hide/remove options from UIActivityViewController
then you can do this using excludedActivityTypes
property of UIActivityViewController
, See following code for this.
let activityController = UIActivityViewController(activityItems: sharingItems, applicationActivities: nil)
activityController.excludedActivityTypes = [.print, .mail, .airDrop, .assignToContact, .copyToPasteboard, .addToReadingList, .markupAsPDF, .message, .openInIBooks, .postToTwitter, .postToFacebook]
present(activityController, animated: true, completion: nil)