As Semphyra stated, it's at online check in. 48 hours before departure. It's nerve racking if you are trying to compete for the upgrade at the 48 hour mark and need to add this info. Be prepared to add passport number, passport expiration date, KTN, emergency contact name and phone number.

My first time flying LA I tried adding it through the call center but the agent insisted I provide an expiration date. After several holds she got someone to add it and it was there when I checked in .. but all the time spent was not worth it when it can be added at check in.