1. Download the rar.file and unzip the files. There should be about a dozen folders and a few hundred map files. The folders contains spoilers so don't look.
2. Scroll down to the end of the map files and you should see an icon of a guy holding a sword called RPG_RT.exe, NOT the one called Setup. Double click RPG_RT.exe to begin the game.
3. (Optional) MS Mincho Font is needed to play the game, unless you want to play with a screwy looking font. Windows XP and higher should contain this font already so you don't need to do anything. If not, you may be able to download it here if you need it, but this site belongs to some guy I don't know so download at your own risk.
(Put it in the /Fonts/ subdirectory of your Windows dir) You may have to reboot afterwards.
4. (Non-Optional) Enjoy the game.
Sidenote: (Optional) I believe the Setup icon is only used to create desktop/start menu shortcut. It is not necessary to use this icon, and I don't recommend doing it unless instructed by me, in case it overwrites some of my game's resources or something.
If you click it for whatever reason, follow these instructions:
Select the folder to install the game to. There are also two additional options that can be selected. They are as follows.
-> Create a Start Menu Shortcut: This will allow you to run the game from the programs section of the start menu. If this is not checked, start the game by double clicking RPG_RT.exe in the folder you installed it to.
-> Add Uninstaller: This will allow you to remove the game using add/remove programs in the control panel. If this is unchecked, remove the game simply by deleting the folder.
Click [Begin] and the installation will start. It should be the left button, if the text is messed up. The right button is Cancel.
Everything is pretty standard console-type rpg controls.
(Up) > [Up arrow key], [K] 
(Down) > [Down arrow key], [J] 
(Left) > [Left arrow key], [H] 
(Right) > [Right arrow key], [L] 
(Decision Key/Talk/Examine/Select > [Enter] [Space] [Z]
(Cancel Key Open/Close menu, cancel] > [Esc] [X] [C] [V] (B) [N]
Note: Numbers refer to keypad. I recommend you play with some kind of controller device if you have one, as it will be kinder to your fingers.
[F4]: Toggles between full screen and window mode.
[F5]: Toggles between normal size and double size in window mode. Sometimes, if the game is slowing down, toggling to normal size or vise versa may help.
[F12]: Returns to the title screen. Use this to exit the game at any time, especially if errors prevent you from moving.
You have 15 save slots so you should save often in multiple slots in the unfortunate case that bugs or errors prevent you from proceeding, as this is an amateur game after all.
The blue glowing circles on the ground are save points. Stand on them and press the action button to use them.
Buy as many food items as you can with your extra money before venturing out into dungeons. Seriously. You'll need lots of food to survive, as monsters deal a lot of damage, so you'll need to heal up after battles.
If you're stuck at a puzzle, try using Special Menu -> Puzzle Skipper when you're standing near the puzzle. Of course, it's better to post on the board asking for a hint first instead of skipping it =)
Please post all technical questions related to downloading or installing the game in this thread.