What you need is a tadpole looking thing like this:
There's no configuration to do. You just plug it in and up pops the screen on your iPad mirrored onto the external screen.
So on to the practical side of finding you a suitable tadpole (by the way not everyone calls them tadpoles, sometimes they are called various adapters, or dock connectors, also with big long descriptions. Tadpoles is just useful shorthand for that type of device). The first thing you need to know, is there is not one type of tadpole, but a whole family of different ones that you need for different iPads and different screens.
Why are there different ones? The connections on either end are different. That's what the rest of this article is about, helping you to choose between the different tadpoles.
30 pin connectors
Firstly the iPad end. If you have an older iPad it will have a 30 pin connector. Even if you have never used a tadpole before, you will recognize the connector from your charging cable. If you charging cable has a 30 pin connector, then your tadpole needs to have the same.
Newer iPads use the lighting connector, which is much smaller and has the gloriously useful trait that you can put it in either way up (if you have ever fought to work out which way up your 30 pin cable goes you will know why that is a fine thing to behold).
Different types of screen connectors
Now we know what is at one end of the tadpole, its time to think about the other. You would think that cables for plugging computers into screens are all the same, oh you poor deluded soul! Although that would seen entirely logical, its not how things are in real life.
What has happened is that over time the manufacturers of screens have come up with new standards to connect things into their screen. New standards that provide higher quality or additional features (like support for HD or sound or 3D). Many screens will have plugs for all sorts of different standards. Look at the back of a modern fancy pants high end TV and shout "what the heck" at all the different types of plugs there. Older screens might just have one input type.
What we have to do it make sure we get you a tadpole which has a right connector for the screen you want to use. Below is a rundown of what you might encounter. Your job is to have a rummage around the back of your screen to see what connectors to have available to plug into. Hopefully the pictures below will help you identify them.
VGA is the oldest standard that can still work on an iPad (there are even older standards like coax and SCART, but if you have a screen that insists on these you need to get a newer screen (yes I know it is technical possible to get an image from an iPad to these using all sorts of Root Goldberg tricks with intermittent boxes, but seriously, the quality is terrible and its not worth it). VGA is the baseline.
You are most likely to use VGA if you have an old screen laying around that you used to use with a desktop PC. Almost every screen that has ever been created for use with a PC has a VGA connector on it.
To get a suitable tadpole go onto Amazon (or similar) and search for "iPad to VGA" and you will be presented with a list of suitable tadpoles, includes ones with both 30 pin and lighting connectors.
DVI sends its information to the screen digitally (instead of in an analogy form), I know, I know, just a lot of technobable. What is means, to normal people, is the picture looks nicer.
If you have a choice to use DVI instead of VGA, use DVI, its better.
HDMI is the standard connector for all modern TV's, DVD players, Set-up Boxes, Games consoles and anything else that puts an image on the screen in your living room.
There are other types of connectors out there, like Display Port and RGB, but as far I can tell, nobody makes tadpoles for them. It would still be possible to get the images onto such screens, but you would have to use extra converters and every screen I have used with such inputs also has one or more of the others listed above that do have tadpoles. So for now, I will say no more on the subject, less lots of you write in and tell me your are desperate for the article to be expanded to cover your particular unusual connection type.
How to select a screen connector type
If your screen has an HDMI port free, use that. HDMI is popular, works well and is on most new screens being made. So not only will your new tadpole work on your currently screen, but you can plug it into most others you either have now or plan to get in the future.
If you screen does not have any spare HDMI ports (either they are already filled with other devices like your DVD players etc, or the screen simply does not have HDMI), use a DVI tadpole. The quality is just as good. It it will work just fine.
If your screen only has a VGA connector (or you have filled all the other inputs with other things), use a VGA tadpole. It's the lowest quality, but if that's what you got, that's what you got, and its still pretty good.
Don't forget a screen table too!
There is one little thing that easy to forget when putting in your tadpole order: the tadpole does not plug directly into the back of the screen. You need another cable.
Fortunately such things are very cheap and you can just throw one into your basket when ordering your tadpole. The key considering is: how long a cable do you need?
A normal screen cable is about 6' long. If you are sitting close to your screen that's going to create a big bundle of spare cable. But if you search on Amazon for "short VGA cable" or "short DVI cable" etc you will see there are little 6" versions that are better suited to this.
If your screen is the other side of the room, you can get enormously long cables to connect. But's its not a good idea. If you want to get the image from your iPad onto your 80" flat screen in the Den. Use an Apple TV. It's a much tidier wire free solution. Sure it costs more than a cable, buts it not crazy money and it does lots of other things as well. The article here for more details. You might even want to use the Apple TV approach for the short range, on your desktop, external screen, just so you don't have to worry about plugging and unplugging cables when you want to use it.
So there you go, now you know what you need to order to get the images on your iPad onto a screen of any size. So now we have blow any one more excuse for you not using your iPad 100% of the time and binning that old PC of yours.