Unlike Yogurtland, Menchie's will be running the promotion the whole day, but you'll need to print out a coupon available on the chain's Facebook page here (you'll need to "like" the page to access the coupon).
The coupon is good for 6-ounces of yogurt and toppings that you put together yourself, choosing from a variety of available flavors and toppings. The coupon is only good on February 6, 2013 at participating Menchie's locations.