1. Let's see an breif introduction of Citra 3DS Emulator for PC first!
Citra is a work-in-progress emulator for the Nintendo 3DS which is written in modern C++ with portability in mind and builds actively maintained for Windows, Linux and OS X. Since it can only emulate a subset of 3DS hardware, it is generally only useful for running or debugging homebrew App. NO commercial games is playable in Citra.
(Citra 3DS Emulator download)

2. Then below is some FAQ about Citra:
What's the function of it?
It can currently emulate ctrulib-built homebrew programs such as Smealum's port of Yeti3DS.

Can I play <insert retail game here>?
In nice, bold letters: No! Citra is not ready yet!. You can not play Pokémon, Super Mario Bros., or any of your other favorite 3DS games yet.

What platforms does Citra support?
Citra works on all three major desktop OSs! Citra is compatible with Windows, Linux, and OS X. In the far future, mobile platforms may be targeted as well.

What kind of specs do I need to run Citra?
Citra currently uses an interpreter to emulate the 3DS's hardware. As one might imagine, this is very inefficient, so it is doubtful that most (if any!) consumer hardware would be fast enough to run at full-speed.In short, there's no real recommended hardware, but suffice it to say that you want the fastest possible processor, and a graphics chip that supports at least OpenGL 3.

Where can I download Citra?
At the moment, there are no stable versions of Citra for you to download. Soon, we'll make available nightly builds for users to download, but for now you'll have to compile from source. Once Citra has progressed to the point where a stable version becomes viable.
More info. can be found in http://citra-emu.org/

3. Lastly, let's see some screenshot about it.