REMEMBER TO INCLUDE THE JS IN THE THEME, SO IT CORRECTLY DISPLAYS THE WYSIWYG
How to set up HTMLArea  with Image Manager for PHPwebsite 9.X: in 10 easy steps.
1) Backup your TextSettings.php file in your conf folder
2) Backup your Form.php file in your core folder.
3) Go to your phpwebsite/js folder and delete wysiwyg.php 
4) Copy the contents of the conf and core folders to the appropriate folders in phpwebsite.
5) Copy the htmlarea folder to your phpwebsite folder.
6) Now you need the absolute path to your phpwebsite files to set up Image Manager.  If this has been provided to you by your ISP, then you are in luck.  If not, and they are responsive, then you can ask them for it.  For 95% of the case, you can do the following (not recommended for production sites):
a) Rename your Form.php in the core folder to something else.  For example, I renamed it to Form.old.  
b) Now browse to your site.  You should get a nasty error message such as:
Warning: main(/home/yoursite/public_html/phpwebsite/core/Form.php): failed to open stream: No such file or directory in /home/yoursite/public_html/phpwebsite/core/Core.php on line 61
Fatal error: main(): Failed opening required '/home/yoursite/public_html/phpwebsite/core/Form.php' (include_path='.:/home/yoursite/public_html/phpwebsite/lib/pear/') in /home/yoursite/public_html/phpwebsite/core/Core.php on line 61
c) This will tell you your absolute path.  In this case, I now know that the path to my phpwebsite files is /home/yoursite/public_html/phpwebsite Don't forget to change Form.old back to Form.php!
7) Open the file config.inc.php in htmlarea/popups  Edit the following to reflect the information you just gathered:
// IMAGE_DIR and IMAGE_URL identify the Image directory "root" (MUST end in "/")
define("IMAGE_DIR", "/home/yoursite/public_html/phpwebsite/images/");
define("IMAGE_URL", "/phpwebsite/images/");
// SCRIPT_DIR and SCRIPT_URL identify where these scripts reside (MUST end in "/")
define("SCRIPT_DIR", "/home/yoursite/public_html/phpwebsite/htmlarea/popups/");
define("SCRIPT_URL", "/phpwebsite/htmlarea/popups/");
Append only the part of the path that reflects your unique website to IMAGE_DIR and SCRIPT_DIR.  Leave the rest of the path as is.  You should only need to change IMAGE_URL and SCRIPT_URL if the folder containing your phpwebsite files is named something other that "phpwebsite".
8)  Once you have saved your changes, you should be good to go.  
9)  If this has been helpful, go to http://www.npowermichigan.org/getinvolved/donations/default.asp and send a donation to the charity of your choice.  
10) Enjoy the good karma of having helped out a worthy cause.
Thanks to Interactive Tools for developing this great tool (http://www.interactivetools.com) and to Gigadev Consulting (http://php.gigadev.us) for their configuration help.