Thanks, guys! I appreciate the responses very much.
Lisa, I didn't see the options you mentioned when I was in the admin area, but I'll look again. I was probably so frustrated that I overlooked it.
Bruce, I'm not familiar with robots.txt files. Do I just write
Disallow: /forum/
on a blank page, save it as robots.txt and upload it to public_html and that's it?
Sorry for the dumb questions, but even though I've been making websites for over six years, I haven't improved much since the beginning.