A while ago, Nintendo announced it's plans for the 3DS Ambassador Program, a scheme in which it rewarded people who bought the console early, before it's price drop on the 12th August, with twenty free games - probably to prevent a second series of, admittedly slightly more nerdy riots stemming from people feeling a bit ripped off. The games come in two separate batches, with ten free NES games kicking off the proceedings from today, and ten Game Boy Advance games available sometime before the end of the year. The program is available exclusively to people who bought the console before the 12th of August - so if you bought it on any day after the 11th August, I'm afraid you've missed out on the free games, although you probably paid a lower price than most of us anyway. Originally, the way to let Nintendo know you'd bought your console before the cut-off date was to pay a visit to the Nintendo eShop on your 3DS (which you'll need to download if you haven't already), which would automatically register you as an Ambassador. Now that the deadline's been and gone, however, things are slightly different.
If you haven't yet accessed the 3DS eShop despite buying your console in time to qualify for the program, there's no need to worry - Nintendo aren't about to lock you out of your opportunity to download the free games. Instead, they've extended the valid methods of registration to include anyone who's created a Friend Code on their 3DS, or those who've simply connected to the internet on it. Your 3DS console's Friend Code is generated when you access the 3DS' Friends List (the smiley face icon at the top middle of the Touch Screen) and register a friend - either locally or over the internet, but in order for Nintendo to realise you've done this, you must have connected to the internet at least once before the 12th August.
If you've done one of the above methods, you'll have been automatically registered for the Ambassador program, and the games will be waiting for you. We've put together a handy guide to downloading your free 3DS ambassador games, too, so you can be sure you get everything you're entitled to.
If you haven't connected your 3DS to the internet, accessed the eShop, there's still no need to worry, though, as there's a final way you can register. Providing you kept the receipt as proof you purchased the console before the date, you'll be able to contact Nintendo, presumably using their Customer Services department's online form, where you'll want to file it under 'Other', fill in the boxes and attach a photocopy of your receipt.
So, there you go. If you've ever connected your 3DS to the internet before, you should be good to go - and if not, you can always send a copy of your receipt to Nintendo - providing you bought before the 12th of August, of course.