You can't do so directly. The plugin only inserts the HTML character encodings into the post body. However, you can use the "Clicking character copies it to the clipboard?" checkbox to copy the character you want to use into the clipboard, which can then be pasted into any other text entry field (in or outside of your browser). Note that the special character (if using the visual editor) or the HTML entity encoding for the character (if using the text editor) will be copied to the clipboard when you click the character.