in your TPP account there is a place to schedule an interview so have a look there - you choose a location, date and then time. Be aware that not all locations have extended opening hours though. Some airports offer 'enrolement on arrival' so check the CBP website to see if LAS offers that and the times as you may not need to schedule an interview at all.
The interview itself was 5-10 minutes but in my case most of that was just general chat.
The interview itself was 5-10 minutes but in my case most of that was just general chat.
Huzzah for International Jet-setting !