Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.
In the interim, after selecting the style sheet from the dropdown, click the Tab key on your keyboard. This will tab the viewing pane and let you click Insert. Screenshot example of screen view after clicking tab.
Note: For Apple/Mac OSX users, you may need to enable the Tab key for switching between dialog boxes and buttons.
To enable the Tab Key for navigating dialog boxes or buttons:
- Launch System Preferences from the Apple menu
- Click on the “Keyboards” preference panel
- Select the “Shortcuts” tab (sometimes called “Keyboard Shortcuts” in older versions of OS X)
- Look near the bottom of the window for a mention of “Full Keyboard Access: In windows and dialogs, press Tab to move keyboard focus between:” and click to select the radio button next to “All controls”*
- Close System Preferences
Reference source: Use the Tab Key to Switch Between Dialog Buttons in Mac OS X