I wish the literal tranlation would be included. "Boarding proceedure" vs "check in".
搭乘 手續을 해주세요.
"Check in please" would be accepted as well, reported on Nov. 30, 2017.
This particular polite imperative with -ju- does not suit the procedure in question nor a prompting for check-in. Something like, please let me check in, would fit better, though the Korean semantics seems a bit overly formal.