The nice feature about this site is you can uplodad pictures into this server. You don't need remote hosting. To do this:
At the bottom of the compose panel there is a button "BROWSE". Hit that and it will allow you to browse your hard drive for the picture.
Once you have found the picture, hit the "OPEN" button, this will bring you back to the message screen.
Then hit "ADD THIS ATTACHMENT". The picture will upload. This may take a few minutes if it is big. Wait for the screen to refresh
Finally, hit "ADD INTO POST" and the system will add a line of code at the bottom of your message. When you view the message, the thumbnail will be clickable to a larger image.