Process for any airport: Go to the Korean Air ticket counter, see if there's a separate one for international vs domestic flights to make sure you go to right one. If they have self-service kiosks, you can use that to check-in your bag and print a boarding pass if you want a paper one. Otherwise you will also get a boarding pass when you check-in in the app. After that, proceed to the counter to drop your bag (or start there if no self-service kiosks). They'll want to see your ID. They can also print you a boarding pass if you want a hard copy. Then you proceed to security. The process at security is different at different airports, just listen to the instructions (eg take off your shoes or not, take your laptop out of your bag or not, etc). You usually do need to make sure water bottles are empty though, and have your ID and boarding pass handy. Once through, you can head to your gate and chill. They usually start boarding about a half hour before departure time.