Ctrip will give you a confirmation number. You take that number with your passport to the ticket window for picking up online tickets. (In smaller stations there may not be a special window set aside for this.) If you go to the wrong window, no doubt you'll be pointed to the right one.

Two caveats. Your actual passport number must match the number in the ticketing system; no match no ticket. Second, I believe ticket issuance stops some time before departure, and the computer just won't spit out the ticket after that. But I think the cutoff point may vary by station in China.