1 Requirements

    Joomla 1.5 or higher installed.
    JCE module with TinyMCE for Joomla.
    A valid license to install the plugin in a production environment; otherwise, you can use the downloaded file just for demo purposes.

2 Copy files

Unzip the tinyMCE WIRIS Plugin and copy the tiny_mce_wiris directory into your Joomla tinyMCE plugins directory. It is usually media/editors/tinymce/jscripts/tiny_mce/plugins but in lower versions can be plugins/editors/tinymce/jscripts/tiny_mce/plugins.

The final directory should be <media or plugins>/editors/tinymce/jscripts/tiny_mce/plugins/tiny_mce_wiris. Now, give write permissions to <media or plugins>/editors/tinymce/jscripts/tiny_mce/plugins/tiny_mce_wiris/cache and <media or plugins>/editors/tinymce/jscripts/tiny_mce/plugins/tiny_mce_wiris/formulas directories to the web server user (it will be used to store formula MathML codes and temporal images).
3 Activate WIRIS plugin for TinyMCE
3.1 On Joomla 1.5.14 or higher

Open plugins/editors/tinymce.php (in Joomla 2.5.x or above this file is inside plugins/editors/tinymce/) and search the line with this text:

$buttons1_add_before = implode(',', $buttons1_add_before);

Now add this code before the line:

$plugins[] = 'tiny_mce_wiris';
$buttons2_add[] = 'tiny_mce_wiris_formulaEditor';  // For WIRIS Formula Editor
$buttons2_add[] = 'tiny_mce_wiris_CAS';            // For WIRIS cas

The final code should look like:

…
$plugins[] = 'tiny_mce_wiris';
$buttons2_add[] = 'tiny_mce_wiris_formulaEditor';  // For WIRIS Formula Editor
$buttons2_add[] = 'tiny_mce_wiris_CAS';            // For WIRIS cas

$buttons1_add_before = implode(',', $buttons1_add_before);
…

The final step is the activation of the extended tinyMCE editor. In Joomla administrator panel, go to Extensions > Plugin Manager and click on Editor – TinyMCE. Now, on Functionality field (on right panel), choose Extended and then save changes.
3.2 On Joomla lower than 1.5.14

Open plugins/editors/tinymce.php and search the line with this text:

$buttons2 = implode(',', $buttons2);

Now add this code before the line:

$plugins[] = 'tiny_mce_wiris';
$buttons2[] = 'tiny_mce_wiris_formulaEditor';  // For WIRIS Formula Editor
$buttons2[] = 'tiny_mce_wiris_CAS';            // For WIRIS cas

The final code should look like:

…
$plugins[] = 'tiny_mce_wiris';
$buttons2[] = 'tiny_mce_wiris_formulaEditor';   // For WIRIS Formula Editor
$buttons2[] = 'tiny_mce_wiris_CAS';             // For WIRIS cas

$buttons2 = implode(',', $buttons2);
…

4 Configure

Edit media/editors/tinymce/jscripts/tiny_mce/plugins/tiny_mce_wiris/configuration.ini to set your own values. This table specifies all possible parameters.
5 Clean and backup WIRIS plugin for TinyMCE