The maps on Magellan GPS devices can be installed through the Content Manager application. This is the software that can be found on the support CD. Connect the device to PC and wait for the registration message. Once it's registered and connected, right click the icon in the system tray and right click it, then select Activate/Download Purchased Content.
You can download it from the official website: http://www.magellangps.com/Content-Manager-Software-for-Windows
Note: Input the serial number of your device to download it for free.