You need to download a pic to a host site. There are a good many free host sites, some are good, some not so good. Here are some that I have used in the past... All of them require free memberships.
http://www.hunt101.com
http://imageshack.us/index3.php
http://www.snapfish.com/
There are more out there if you look for them. Once you join you can download pictures easily via their instructions. Once you do that each picture will have a web address such as .....
http://www.hunt101.com/img/028014.jpg
Copy and past that address to here, and click the Img button above then paste the address, and then click close tags. Or you can type [img](paste%20web%20addy)[/img]. Should look like this when you are done...
Hope this helps.