I decided to improve (I think) my tutorial. I thank Rich Hanover for some tips. Here it is:

Here is how to put pictures into your posts on this board. You type the formatting, discussed below, within the text of the body of the post; you do not put it into that "Optional Image URL" box! (The Optional Image URL box is fine if you just want to post one picture.)

First, you have to get picture URLs. One way is to have your own pictures and then use this board's "file upload" link to have this board host the pictures and provide you with a jpeg URL. Another way is to copy someone else's jpeg URL (from eBay, for example). Here are three jpeg URL's that I will work with here (click them and see):
http://www.antiquegamblingchips.com/crest/bison.jpg
http://www.antiquegamblingchips.com/pictures/arab.jpg
http://www.antiquegamblingchips.com/pictures/aguac4.jpg

Let's start out easy with one picture: (1) click either "post new" or "reply," (2) type (or copy/paste) this in the "message" box: [pic]http://www.antiquegamblingchips.com/crest/bison.jpg[/pic] , and (3) click the "preview" (or "post") button, and, Presto!, the words "[pic]http://www.antiquegamblingchips.com/crest/bison.jpg[/pic]" disappear, and the picture of the bison chip appears:

If you want to show three pictures, place (type) each jpeg URL between "[pic]" and "[/pic]" like I did here
[pic]http://www.antiquegamblingchips.com/crest/bison.jpg[/pic]
[pic]http://www.antiquegamblingchips.com/pictures/arab.jpg[/pic]
[pic]http://www.antiquegamblingchips.com/pictures/aguac4.jpg[/pic]
Click "preview" and see pictures instead of words:

If you want to center the pictures, type this:
[center][pic]http://www.antiquegamblingchips.com/crest/bison.jpg[/pic]
[pic]http://www.antiquegamblingchips.com/pictures/arab.jpg[/pic]
[pic]http://www.antiquegamblingchips.com/pictures/aguac4.jpg[/pic][/center],
And then click "preview" and get this:

If you want to see the pictures side-by-side, type the three sets of [pic]url[/pic]'s side-by-side (one after the other with no spaces) as such:
[pic]http://www.antiquegamblingchips.com/crest/bison.jpg[/pic][pic]http://www.antiquegamblingchips.com/pictures/arab.jpg[/pic][pic]http://www.antiquegamblingchips.com/pictures/aguac4.jpg[/pic] ,and after you click "preview," you get this:

([center] and [/center] tags would center them.)

Robert (P.S. if something is not clear, or you see typos, errors, let me know, thanks.)