Tell us when you are coming and what you want examined. What comes back is a named program at a named partner centre, at a fixed price held for 60 days. No account, no card, and no charge until you arrive in Seoul.
Most of this is quick. Two answers do real work, so they are worth reading before you tick them. Sedation, because a gastroscopy and a colonoscopy are performed under it at every partner centre and your answer decides what the day can contain. And medication, because blood thinners and diabetes medication both change what can safely happen on the day. If you take nothing, say so explicitly. A blank answer and "nothing" are different answers and only one of them is safe to act on.
Dates need about two weeks of notice. The tests inside a program are sequenced around the appointment, so a slot has to be held rather than found on the morning.
What happens to what you send, how long it is kept and who sees it: the privacy page says, specifically.