I think you are close, but not quite there...
ok I have a full copy of forum under www/forum
This may be correct, let's just double check to be sure... If you were to unzip the forum plugin distribution, it would look like this:
PHP Formatted Code
What you want to do is copy all the files in the public_html
directory in the forum distribution into your www/forum/
directory (remember you had to create the forum/ directory first).
I copied just the admin file to www/admin/plugin
You need to copy forum/admin/*.* to www/admin/plugins/forum/, so you first had to create the directory forum
Looking for theme directory, under layout?
as in www/layout/professional/
Now you're talking! You want to copy all the files from the themefiles
directory in the forum distribution to the www/layout/professional/
I think you are getting close!