Wilbur-

Here's the basic process:

1- Host your picture on the web somewhere. I generally use ImageShack to host pictures so that I can post them on boards.

http://imageshack.us/

Conveniently, there are a number of resize options before you click the "Host It!" button.

2- Find the exact URL of the image and copy it into your clipboard. This should be something like:

http://img79.imageshack.us/img79/9664/img5877xw3.jpg

(it should end in ".jpg" or ".gif", NOT ".htm" or ".html")

If you use ImageShack, it will be the LAST URL they list after the upload process is complete

3- Use standard html protocol for posting pictures. A GOOGLE search will pinpoint several tutorials on the web. For instance

http://www.htmlgoodies.com/primers/html/article.php/3478181

Essentially:

{img src="http://img79.imageshack.us/img79/9664/img5877xw3.jpg"}

where the first character is replaced with the "less than" symbol, and
the last character is replaced with the "greater than" symbol

If I type it correctly it should display the imaage corresponding to the image URL I've used as an example above: