Chances are you are on a network and using a router
You have to access the router and forward remote access controls to the computer and port you want. Refer to the user manual. It is common for the port forwarding setting to be found under firewall. If you don’t have the option to directly select your computer type in the IP address and then enter the start and end port number. You may have an option for WAN and Lan and the protocol. TCP is the default setting.
Windows 8 Pro is required.
Change the port that Remote Desktop Connection uses (or “listens on”) from the default port 3389. When you log on, type the remote computer name, followed by a colon and the new port number (for example, MyComputer:3390)