When using the
MSSticker(contentsOfFileURL: stickerURL, localizedDescription: localizedDescription)
to create a sticker, how can you input a url to an external source where the images are stored?
You cannot. The URL has to be a file: URL. If you want to use image content that is external then you would need to first download that, store it somewhere on disk and then use a file URL to where you stored that image.