User dictionary file can be copied manually. Please follow these steps to import.
1. Copy VOCALOID2 user dictionary file (*.udc) to other place (i.e. desktop).
* .udc is hidden file, so please change the settings of the explorer so that it shows such file. And *.udc file is located in the following folder.
2. Open copied dictionary file with your text editor which supports unicode, and save the file with another name and unicode encoding.
3. Place the file saved in step 2 to the following folder.
4. Launch VOCALOID3 Editor or Tiny VOCALOID3 Editor and click [Lyrics] → [User Dictionary] → [English] from the menu bar to show user dictionary dialogue.
5. Select the file copied in step 3 on "User Dictionary" combo box, and click "Close".