i will do the best to tell you installation and running. the following is told to you by a 12 year old:
1)go to
http://mythruna.com/download-now/ and select your system for download.
2)extract to location you want it to go.
3)go to that location. if you run on windows and you use the "search" and mythruna is listed under programs that link will not work. all files need to be located in one spot.
4) double-click on the application "Mythruna-20120627" a menu will pop up. the farthest left is a dropdown. best for that is either size "800x600" or "1280x720" fullscreen i do not reccomend, such as if you were to check something on the computer. you cannot resize the client after you have chose your settings and clicked "ok".
The rest should be easy to figure out. WASD to walk, Arrow Keys or mouse (or mouse pad) to move visual angle. press F1 for other questions while in either single-player or multi-player. if you want to play on a multi-player server click on multi-player and there is a built-in server name and address that will always be there.