I just did this from my Ipad...assuming it works the same..go down to .Go Advanced.....vvvvv below.
Click that..then you will see manage attachments...click that...you will see a bunch of oval bubbles that say choose file...click the oval bubble...Then Choose Existing...click that. Then you should see your camera roll..choose your pic..then you will see upload ..bottom right. Choose that. You can repeat for more than one picture..then close the window and submit reply!