I got 99 problems but my WiFi ain't one

OK, this all sounds like you are getting into quite a muddle.

There is quite a lot of ground to cover here and underlying knowledge, which whilst not totally necessary woukd make your life a lot easier.

I'll try to lay it out in a simple way and see if it helps. (Best to read it all once through before trying to do anything, as I have not managed to get it all into a linear fashion):

You will have two (or maybe three) networking devices on your network:

1) your main router (which will be performing quite a few functions: routing, handing out IP addresses, being a firewall, possiby being an ADSL or cable modem, being a switch / hub and being a wifi access point) - We will call this "Router"

2) your secondary "router" which will not actually be acting as a router or anything else, just as a wifi access point. We will call this WAP (Wifi Access Point)

3) (Possibly a seperate modem that sits between the internet and your router, via the WAN port on the router. However, given your posts above about the WAN port, I am betting you do not have a seperate modem. Your router wil be doing this job.)

Firstly, you want to get your WAP setup as just a WAP. How you do this varies between devices, but in essence you need to access its settings page, turn off its routing capabilities and its modem (if it has one). Then configure its Wifi part to have the same SSID (network name) and password as your main wifi network that your router is also serving up.

Also, on the WAP settings, configure it to have an automatic IP address, not a fixed one. Be careful there are dragons here: You need to be setting the IP address of the WAP via its own settings page, not setting up the configuration of the DHCP IP address allocation serveron the WAP. (see below for more info)

Once you have this done, connect it via an ethernet cable to one of the switch sockets on the back of your router, not the one labelled WAN. In the completed setup, this is via two cables: one from router to the wall port and then one from the other wall port to the WAP.

Now, note that once you have this configuration, we should pay attention to IP addresses.

Each device on your network has an IP address and typically, that address will have been handed out to them via a protocal called DHCP, by your router. The router itself has a fixed IP address, usually something like 192.168.1.1 or 192.168.0.1

If you have managed to get this all setup correctly, your WAP will now have an IP address that has been given to it by the router, which will NOT be the one that is written on its back or in the manual or whatever. You can find out what its address is by looking at the router's web page. There shoud be a list of "connected devices" or similar. Once you have ascertained the IP address of the WAP, you should be able to use that in a browser to access its settings page, in case you need to tweak the WiFi settings.

If you get this far it should all be working. You should be able to walk between the rooms and seamlessly connect to wifi. The only gotcha is that if your laptop or tablet or phone or whatever stays on the "other" wifi access point and is slow. You can just turn wifi on and off on the device if this happens, it should then reconnect to the strongest / closest access point. (More advanced networking kit allows you to configure signal strength management that negates the need for this.)

One more thing to mention. If it is all up and working, you should be able to plug ethernet devices like laptops, PCs, TVs and games consoles into the ethernet ports on the back of your router or WAP, in either room (not the WAN port).

Phew, I hope that helps. If you need it I can draw a little sketch, but I am supposed to be on holiday here in Center Parcs and the kids are getting up...