You have a couple options to display pics here. One - you need to upload them to a photo hosting site like flickr, then copying and pasting the image url address of that pic into the image tags by clicking on the little button that looks a bit like the Mona Lisa. It will place the image tags on your screen and paste the url in between them.
it would look like this (i made up a generic image url for the example):
[ img ]www.flickr.com/xxxxxx.jpg[ /img ]
The 2nd, quicker way is, when you have your posting window open, click on " +Attachments and other options" right below the message window. You can then browse, select and add pics directly from your phone or pc that way: