(Based on the tutorial at http://www.nisus.com/ Nisus Software, Inc)
Korean Language Kit comes with MAC OS X (from 10.1.x). To install Korean Language Kit on the MAC OS X, please follow the instruction.
To install it,
1. Click on "System Preferences"
2. Then click on the "International" icon.
3. Click on Keyboard Menu tab.
4. Check the boxes next to KOREAN.
5. A US flag should appear in the taskbar at the top of your screen.
6. Click on the flag to get the drop-down keyboard menu and select the KOREAN keyboard
Korean Language Kit comes with MAC OS 9. To install Korean Language Kit on the MAC OS 9, please follow the instruction.
1. Double click the Mac OS Install icon on the Mac OS 9 CD.

2. You will see a "Welcome" window. Click "Continue".

3. Choose the hard drive on which you want to add the Language Kits.

You do not want any of the "Options..." available here. These allow you to create a new System Folder on your hard drive. You do not want that. You want to add software to your current System Folder. If you click the "Options..." button, you'll see:
Click "Cancel".
4. Then click "Select".

You see, the installer has checked and found that you already have Mac OS 9 on the disk. You want to add software features to your System.
5. Therefore, you click: "Add/Remove".
Now you see the "Custom Installation and Removal" window.
You have a lot of options here. But, all you want (now, for our purposes) is to scroll to near the bottom of the list where you'll see "Language Kits".
6. Check "Language Kits" and notice that the pop-up menu to its right becomes enabled:

7. Click the pop-up menu and choose "Customized Installation...":

A new window opens in which you can check off the specific language kits you want to install:
8. After you check off the Korean Language Kit, click OK and then you're ready to install it.
* ALTERNATIVES:
If you want to install Korean Language Kit directly from the MAC OS 9 CD, You can open "MacOS 9: CD Extras - Language Kits - CD Extras - Language CD Extras README" and follow the instruction about how to install the disk image file.