Backup your "Interface" folder and "Fonts" folder if you have one. Then place both the "Interface" and "Fonts" included in the download in your WoW folder. Some aspects may be out of place and requires moving but should work fairly well on any screen resolution.
If the text on the pet frame is off try changing the unitframe status text to show just Percentage (Interface>Status Test>Dropdown at the bottom
Make sure to turn off the border on the default raid frames and set Adapt to square portraits if not matching UI Style