authentication of degree certificates for a foreigner in Korea

I cannot find the web page where I can make an appointment for the authentication in Korea.
Can I just drop by the Chinese Visa application service center in Seoul without an appointment for the authentication of the diplomas obtained from a foreign country?

I do not need the visa at this stage, and I just need to email them the authenticated diplomas. I graduated from the schools in the USA, and I need to have my diplomas to be authenticated.