Go here: https://github.com/smealum/regionthree/ and scroll down for the instructions
Edit: forgot to say, the exploit website he is refering to is: "http://go.gateway-3ds.com/"
For best results, make sure to clear your 3DS's browser history and cookies (tap the wrench on the 3DS browser menu).
If you have issues, check the release topic here (note, I had nothing to do with it, I'm just posting about it here 'cause I assume it should be useful to several of you) : http://gbatemp.net/threads/release-regionthree-region-free-loader-for-3ds-2ds-xl-from-9-0-9-4-sky3ds-users-regionfree.378975/
Quoted from the FAQ:
FAQ
Does this work on the latest firmware version ? Yes, 9.4 is supported.
Does this let me run homebrew and/or roms ? No, it just lets you run legit
physical games from other regions.
Do I need to connect to the internet every time I want to use this ? Yes.
Do I need a flashcart/game/hardware for this ? No.
Will this work on my New 3DS ? No, at the moment this only works on 3DS,
3DS XL and 2DS models.
Will it ever work on the New 3DS ? Maybe. I don't plan on working on it,
like, ever, but the code is out there now so...
Will this break or brick my 3DS ? No. There's virtually 0 chance of that
happening, all this runs is run of the mill usermode code, nothing dangerous.
Nothing unusual is written to your NAND, nothing permanent is done. With that
in mind, use at your own risk, I won't take responsibility if something weird
does happen.
As he said, It shouldn't at all be dangerous, it doesn't mess with the firmware (it just force-loads the games) but I also take no responsibility if something wierd does happen.
I haven't tested it myself, but as far as I've heard it works near-perfectly, the only problem is that you can't open the Home Menu from within games, you have to shut down the 3DS first (at least with Smash Bros.) so no Miiverse.
Note however that this will likely void your warranty, I'm not sure if it's use is detectable (It probably is, since the games might show up in your play record)
Enjoy!