How to set up "Free Shipping" method

I have tried to set up a free standard shipping option, by putting 0 in the “rate value” filed, the option will not be shown up at all in the “calculate shipping cost” page ; I have to put a non-zero value as 0.01 to make the option shown, which is weird in a customer's view. Cs-cart V3.0.3 professional. Any help will be appreciated.

Don't bother, I just read the KB and figured out how.