The easiest way to post pictures is to click on the "insert image" icon (looks like a square painting to the left of an icon that looks like a roll of film).
Then click on the "from computer" tab and then click on "select files".
Then navigate to the folder where your pictures are and select one or more and click on open.
Then click on "upload" and post the reply.
Let me know if you have any problems with this.
There is an image size limit (file size, aim for around 1 meg maximum to be on the safe side)
Steve B