On-Q LeGrand Home Network -- Need Help Please!!

Well, no one else has commented yet, so I'll try to help, but I'm a bit confused. You said you have an "On-Q" at home. What, exactly, do you have? I've done quite a few wiring jobs, and I'm familiar with the brand (in fact I just bought some Legrand/On-Q wall ports and plates this weekend) but to me they're a brand, not a specific item.

Are the yellow cables terminating at one point in your house, but they're just not connected to anything? Are the cables coming from different rooms in the house? Where are they terminating to - a closet, or a room? Are there electric plugs nearby? If that's the case, you have a few options at the termination point:

1) Get a patch panel and wire all of the yellow cables to the patch panel. That gives you a nice, clean place to plug in cables from a switch.
2) Connect wall ports to each one and have wall plates. I think they only support up to 6 ports per plate, so you could do 2 1-gang options with 2x 4-port plates. It's basically the same idea as the patch panel, but using wall ports & plates instead of a patch panel.
3) If the cables are long enough, and if making them tidy isn't as much of an issue, then you could just terminate each cable with an RJ45 connector and plug them straight into a switch.

Once you have that settled, and as mentioned in the steps, you'll need a network switch, which will need to be powered - which is why I was asking if you had an electrical source near the termination point of the cables. You can get a switch on Amazon.com or buy one at a local electronics store. I wouldn't buy one from the hardware store - for some reason all I ever see there are 10/100 switches and they're way overpriced. You can get a nice 8-port gigabit switch for ~$30 on Amazon. However you decide to terminate the cables, you'll need to eventually plug them into the switch to get them to all talk.

You'll want to know which cable is going to which room, and to somehow label your patch panel / wall panel / individual cables (depending on how you choose to terminate) accordingly. And yes, to do so all you really need to do is plug something into each one at a time and see what port lights up on the switch. Technically it doesn't really matter if you label them, I suppose, but it's nice to know what's coming from where so that you can troubleshoot problems later on. (I only say it sort of doesn't matter if you label because whether or not you know where they're coming from and what's on the other end, you're plugging all of them into the switch indiscriminately, so they'll operate correctly whether or not you label them. It doesn't matter if the router is plugged into port 1 or 4 or 8 on the switch, it'll just work.)

As far as your router is concerned, you are correct: once the network cables are all terminated and connected to a switch, you should be able to simply connect the router to the wall, which is connecting it to the switch. Most routers have a network port or a 3 or 4-port switch built-in; just connect that. The router will then handle assigning IP addresses to all the devices on the switch.

Yes, you can connect a wireless access point into one of the wall ports that are wired to the switch, and extend wireless to that section of the house. By connecting to the switch, which is connected to the router, you're effectively extending the reach of the router to that location. If you're using another "router" be sure to put it in bridge mode so it isn't assigning IP addresses to clients connecting to it. You'll want it to pass on whatever addresses are assigned from the router.

As a side note, *theoretically* you should be able to name the SSID the same on all the wireless access points; that way your clients can move from one area of the house to the other without having to actively change their SSID. I've done this in practice successfully in the past, but it's been a while. I'll be trying it again when I do my wiring project in a week or two. Someone may challenge me on that, and all I can say is that I've done it before and it worked exactly how I wanted it to. In fact it was for a house that was similar to what it sounds like yours is: there was a wifi AP downstairs and one upstairs, and the owner wanted to move from one to the other seamlessly. The client device would connect to whichever was stronger.

I hope that makes sense and is helpful.