To vote, you must first register for an account. It only takes a minute, and is pretty painless. Where it becomes a little confusing, is that they ask for an NRIC number (Singapore ID card), and a telephone number. I guess they weren't expecting many non-Singaporeans to be voting, but luckily you can just put and #'s (9-10 digits) in those fields and the registration will go through.
If you see a Chinese only error message it means you did the captcha wrong - just go back and try again. Also, keep an eye out for the registration confirmation email. Mine hit the Spam folder in Gmail, so you might need to look there for it.
Once registration is complete you can go back and vote every 24 hours. I would be very appreciative if you did, as the grand prize is a trip to Australia, which would mean even more McDonald's for me to review!