I have issues with this too, I am unsure if you can.
I think the only way you can do it is to get flicker or such app and upload them to there. Then copy the url and paste it into your post.
We are upgrading to a new forum software soon which has tap talk built in for mobile devices. Basically it cuts the forum down for phone to make it more useable, I am sure they will have addressed this feature in it.