Modifying a Hanja word is similar to the process for adding a Hanja word.
Select a Hanja word from the User Dictionary and click the Modify button.
Edit the Hangul associated with the Hanja in the Add/Modify dialog box. Then use Control-K to commit the Hangul characters you want to associate with the Hanja.
In the Hanja field, type the Hanja associated with the modified Hangul.
Use the character-by-character methods described in Using Hangul/Hanja Conversion to Enter Hanja.
Click the Modify button.