I have the full version of Radmin viewer and server, I can connect with IP address within my home network, but when I want to use it with a different computer outside, the same IP address doesn't work. Someone said I need to forward my ports or something, Can anyone help me with this? Thanks.
your internal network uses private IP addresses. Most likely 192.168.1.x
From your home computer, visit the website whatismyip.com - this will show your publicly visible IP address. Your router is the translation/path between the public and private.
You will need to set up your router so that someone visiting the public IP address say on port 1234, is trying to reach the server (say private IP 192.168.1.5) - it will forward the traffic to that computer. How you do that exactly depends on the brand/model, but it should be in your user documentation. There should be an admin web page for the router, look for a port forwarding section - there should be online documentation.
Since your public IP address can change over time, assuming you aren't paying your ISP for a static address, some routers can register with public dynamic DNS services, such as http://www.dyndns.com/
Thank you gtvr for your reply i have looked around but i can't seem to get it working. I have the Netgear GS108 Prosafe Gigabit Switch, is that my router? If it is, could you please tell me how to do it? Thanks in advance.
no, that looks like just a switch. There is probably a cable modem or something attached to it that's a router. You can usually manage it, if possible via web, by going to the address of your default gateway
look at 'default gateway' - say 192.168.1.1 for example
type that address into your web browser