Update README.md

Author: jtreanor

README.md

@@ -36,7 +36,7 @@ This step is required to work around an [App Store submission bug](http://www.op
 
 When installing Intercom, you'll need to make sure that you have a `NSPhotoLibraryUsageDescription` entry in your `Info.plist`.
 
-This is [required by Apple](https://developer.apple.com/library/content/qa/qa1937/_index.html) for all apps that access the photo library. It is necessary when installing Intercom due to the image upload functionality.
+This is [required by Apple](https://developer.apple.com/library/content/qa/qa1937/_index.html) for all apps that access the photo library. It is necessary when installing Intercom due to the image upload functionality. Users will be prompted for the photo library permission only when they tap the image upload button.
 
 ##Example app
 There is an example app provided [here](https://github.com/intercom/intercom-ios/tree/master/Examples) for both Objective-C and Swift.