Here's a short tutorial on how you can insert a picture and image.
First, you need to know the web address or URL of the picture you want to insert. If the picture is in your computer hard disk then you need to upload it to an online photo sharing site e.g.
Flickr.com or
Photobucket.com. I prefer to use Photobucket.com for pictures at forums. Once you uploaded your pictures to Photobucket, you will be given an URL to the picture.

Click at the IMG Code and paste it here. That's all. Very simple!
And here's a YouTube video to show you how to do it...