Hi,
Enabling Remote Management allows you to manage the router from anywhere on the Internet. Disabling Remote Management allows you to manage the router only from computers on your LAN.
Remote Admin Port is The port that you will use to address the management interface from the Internet. For example, if you specify port 8080 here, then, to access the router from the Internet, you would use a URL of the form: http://Wan IP Address:8080/.
You can get Wan IP Address from your routers Status Tab Under Wan Settings, once you log in using the default IP Address http://192.168.0.1.