Darren is correct. You come off your flight, head down the hall toward immigrations and branch off at the transit sign just before the escalators going downstairs to immigration. It is very well marked; you won't miss it. There, you go thru a security check point and take escalators to the floor for the departing flights. The LanChile and the AA lounges are fairly close together, so you will have your choice if your status or class of service gives you access. The airport is nice, modern, and very pleasant.