GunZ The Duel is a third person shooter game that requires fast reflexes and dexterity. At first, many things will seem hard, but the key to execution is practice; you won't be able to get everything down first time, so don't quit early.
So, after downloading the game, installing it, logging in and patching the game (if you're playing ijji's North American version of GunZ), select a server and click connect (do NOT hit enter, as holding it down will automatically exit you out of the game). You will arrive at the character select screen; make a character if you haven't already, and log in.
You are now at the channel lobby. The server name and the name of the channel are listed at the top left of the screen. As well, shop, inventory, channel and options buttons are also at the top. The shop is where you buy and sell items (do not sell items EVER with few exceptions, however). The inventory is where all of your equipment and quest items are, and where you equip stuff. The channel select is where you select your channels - for now, you can only go into the free channels and entry level channels, as well as the private and clan channels, accessed by clicking the buttons on the side. The options button is your basic options; as a recommendation, use a 16 bit resolution, as most older graphics cards get FPS (frames per second) lag on a 32 bit resolution; the lower amount of colors does not affect the in-game graphics much if at all.
Korean Style, or K-Style, techniques are used to improve your playing speed via cancelling (see the techniques page for a list). The simplest practical technique which should be learned first is the Butterfly aka bf, which allows you to move gracefully attacking and defending. Use this to practice to get a feel for the game.