Leo,
If you have the pic save to your computer it's real simple...
Write your post, then down below the window you write in, you will see "Attachement... Click here to choose your file"... click on that, a small window will pop up. Click jpeg picture, then click on 'browse'. Your files will pop up in that window. Scroll thru and find the pic you want, click on it, then click "Upload"... give it a few seconds.. and it will come up and tell you the pic has been uploaded, "click here to close window"
Then, just post the message. NOTE: The pic won't show up in Preview, but will show up in the post.
Dreamer