This Document was graciously provided by Sandee Cohen...
Sandee is author of Fireworks 4 VQS, FreeHand 9 VQS, InDesign 1/1.5 VQS, and co-author of Real World Adobe Illustrator 9 and The Non-Designer's Scan and Print Book. http://www.vectorbabe.com
Instructions for installing extensions in Dreamweaver for the Mac.
If you double-click the .mxp file and it does not install into Dreamweaver, there are two routes you can use to fix the problem.
File Exchange Fix: If your system does not recognize the Extension file format (MXP), it may try to launch Simple Text to open the MXP file. That won't work.
Go to Control Panels > File Exchange > PC Exchange and add file type: mxp. Browse for the Extensions Manager program. The file should now be recognized. If not, try the next solution.
Dreamweaver Fix: Launch Dreamweaver and then choose Help > Manage Extensions.
This opens the Macromedia Extension Manager.
With the Extension Manager open, choose File > Install Extension.
Then use the dialog box to navigate to the folder on your hard drive that contains the MXP file you want to install. Click the Open button.
Read the disclaimer and then click the Accept button. (Hang in there. You're almost done.)
Wait until the progress bar is finished and you get notification that you've successfully installed the extension.
The extension will now appear in the Extension Manager.
Relaunch Dreamweaver for the extension to appear in the Dreamweaver menus.