Asking Information for Apply Visa

Dear Sirs,

I am Tuan, come from VietNam
i am a graduate student in ChungAng univeristy, Korea (Visa D -2)
Next month, I have a conferences in Wuhan, around 5 days
Could you give me the exact procedure to follow (requirement document, location for coming...)
Do i need an invitation letter from the host of the conferences ?

I am very appreciated your time.
Best Regards,
Tuan !