You can insert images linked elsewhere from the web using image icon in the tool bar. You'll need the URL to that image.
You may also attach images to your post which can be uploaded from your computer.
If you see the " More Reply Options " button when composing your message. Click it.
Then down below under Attach files Click "Choose File" then "Attach This File".
Once your file (image) has been uploaded you'll then have the option to "Add to Post"
Add to Post will insert some BBCODE to the attachment. You can move that around anywhere in your message where you would like it displayed.
You can add multiple files and add them to your message.
Not adding the file to the post will simply include the file at the bottom of you message as a thumbnail.
Clicking on the thumbnail will open it in the viewer.