check in
phrasal verbcheck in (at…)  
- to go to a desk in a hotel, an airport, etc. and tell an official there that you have arrived
- Please check in at least an hour before departure.
 - We've checked in at the hotel.
 
 
check something  in  
- to leave bags or cases with an official to be put on a plane or train
- We checked in our luggage and went through to the departure lounge.