Apostille Process for a U.S. Master's Degree Certificate (Non-U.S. Residents)

[as4300]

I graduated from Columbia University, and I’m now looking to apply for a PhD in South Korea. As part of the application, they require my Master’s degree certificate to be apostilled. However, I no longer live in the U.S., so I’m not sure about the best way to get this done.

Has anyone here gone through this process before or knows how to do it? I'd really appreciate any guidance or advice. Thanks in advance!