AUTOMATIC INSTALLATION
Step 1: Download and install ZXP  HERE  or  HERE
Step 2: Open ZXP Installer and select the downloaded Magic Retouch Pro zxp file from Automatic Installation folder.
Step 3: Launch Photoshop and go to Windows>Extensions>MagicRetouchPro.
Step 4: Open Retouch Preset in Photoshop from Retouch Preset Folder.

MANUAL INSTALLATION
In case you are having difficulties using the automatic mehtod you can install it by using the manual method below.
Step 1: Open the Manual Installation folder from the Magic Retouch Pro package which you downloaded.
Step 2: Copy MagicRetouchPro folder from Manual Installation folder and paste it to the following directory

Windows 64:
C:\Program Files (x86)\Common Files\Adobe\CEP\extensions\
Windows 32:
C:\Program Files\Common Files\Adobe\CEP\extensions\
If the Adobe\CEP\extensions folder does not exist, you can create it.

Relaunch Photoshop and go to Windows>Extension>MagicRetouchPro

OSX

Step 1: Open folder /Library/Application\ Support/Adobe/CEP/extensions/ or you can open this folder via terminal by entering "open/Library/Application\Support/Adobe/CEP/extensions/" command without quotes.
Step 2: Navigate to the downloaded Magic Retouch Pro folder, then go to Plug-In>Manual Installation and copy folder MagicRetouchPro and paste it in /Library/Application\ Support/Adobe/CEP/extensions/ folder.
Step 3: Relaunch Photoshop and go to Window>Extension>MagicReotuchPro