If they are stored on your own computer then it is very easy, just click the Add image to Post link at the bottom left of the text editing pane - that is where you write your messages.
Then follow instructions - that's all!
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HOWEVER
If they are already somewhere on the web but you haven't got them on your computer - they might be on your website for example - then you can use the BB [.Image] code to show it on the page. Here's how:
Make a note of the URL or address where the picture is located.
Now if you look at the top of the text editing box where you type in your messages you will see a button marked Img which stands for Image. Hover the cursor over this and see the instruction:
Insert image:
Click the Img button and the opening tag will appear.
Instead of .http://image_ url you must type in the address where your picture resides, and its name. For example it might be:
.http//www.mywebsite.co.uk/mypicturefolder/punchpicture.jpg
You would then insert the closing tag [/img]
Another way is to first insert the picture_URL, then highlight it. If you then click the Img button the tags will be applied.
.Now here is an example assuming you haven't got the picture on your computer but it is elsewhere on the web.
I have a picture called hammer.gif which I want to show you. The address where the picture is located is :
[.img]http://www.dogtoby.co.uk/images/hammer.gif[/img]
I then type or paste this code in here:

Success!!
NB You should make sure that your file names do not have blank spaces in them.
eg: My picture.jpg is bad, Mypicture.jpg or My-picture.jpg is OK