I am A Mexican with Korean Working Visa type F, I would like to Go to China for Bussines Trip

I am a Mexican Citizen with Korean Working entry permit. I need to go to China for Four days, I live in Suncheon, where is the close office to do the tramit. Now I have the following Documents

MExican Passport
Korean Working entryp permit
Invitation Letter from a Comercial Supplier

Please tell me how to proceed and if I need additional documents and time of entry permit delivery, I need to go As Soon as Possible.