You need a basic understanding of what you’re trying to do. Your manual may assume you already have that. So, to quote myself elsewhere:
For most, but not all router firewalls, (some work a little differently), they will not open a port universally. That potentially creates a huge security hole for any device that was relying on the port being safely blocked.
Therefore, most routers requires that you specify a particular IP address at which you want the port unblocked. Your computer must be at that specific IP address. If it’s at another address, well, the port will be blocked for that address.
This is why you need a static, unchanging IP address, for the computer, on the local lan which is created just by having the router in the hookup.
This local lan probably uses one of two address blocks which are specifically reserved for private LAN’s and are not valid out on the internet at large.
The first and largest block is 10.xxx.xxx.xxx That’s called a “Class B” block and can have 256 * 256 * 256 = 16 million different addressable devices in its network.
The second block is at 192.168.xxx.xxx, a “Class C” block, and can have 256 * 256 = 65 thousand devices in its lan.
Most people, especially at home, don’t use anything like that many devices of course. Two or three is more usual. But all those addresses are available to you behind your router. They’re also available to your neighbor behind his router, on HIS lan.
The front side of your router, called the WAN side, connects to the internet. It has its own IP address, which it gets from your service provider. The router does address translation and keeps everything straight.
From my point of view, here on the far side of your router, every computer in your house seems to have one single IP address, which is that of the router’s WAN side. If you visit whatsmyip.com it will tell you your IP address is likewise, your router’s WAN address.
If, on the other hand, you give your computer the shell command, “IPCONFIG”, then it will tell you the computer’s IP address on the local LAN, which will probably be in one of the reserved blocks I mentioned earlier. Whenever you seen an IP address that starts with 10, or starts with 192.168, you know it’s on a LAN and if it’s connected to the internet at all, that connection is through a router.
By default and without a router in the middle, your computer asks your ISP to lease it an IP address, using a protocol called DHCP.
With a router in the middle, your computer snivels and asks the router, “Please, sir, may I have an address, sir?”, and gets the back of the router’s hand, and an assigned address on the lan, out of whatever block the router’s using. So for example, the computer gets 192.168.1.27 temporarily leased to it. Temporarily, meaning that it can and does change, even in mid-session, and next time you reboot the computer or the router, you might get a different address.
Now on the other hand, the computer swaggers up to the router, pokes it painfully in the chest and says, “I’m using 192.168.2.5. Got it? Punk?”
“Um, but …”
“Yeah? Punk?”
“Err, nothing, sir.”
In this situation you set your computer to use that specific address, which it asserts on the LAN. It is your responsibility as admin to make sure no other device on your lan tries to use that same IP address, or Bad Things Will Happen. This address does not change, because it wouldn’t dare. It’s static, fixed, and you can forward the port in the router’s firewall to it.
This process is manual configuration, and is what UPnP for a router is essentially supposed to automate on those few occasions when it is implemented correctly and actually works.