From: http://www.koreanair.com/local/na/en...ortService.htm

What are the eligibilities for Korean Air Lounges?

Korean Air Lounges are available for Korean Air First / Prestige Class passengers, SkyTeam First / Business Class passengers, Million Miller Club / Morning Calm Premium Club members and SkyTeam Elite Plus members.

Skypass Million Miler Club / Morning Calm Premium Club members and SkyTeam Elite Plus members are allowed to invite one guest per person traveling on a same day Korean Air or SkyTeam flights.
KAL First Class Lounges are available for Korean Air First Class passengers and SKYPASS Million Miller Club / Morning Calm Premium Club members traveling on Korean Air Prestigae Class only. (KAL First Class Lounge is currently available at Incheon, Tokyo - Narita, Osaka, Los Angeles, New York - JFK Airport)
Lounge Passes will be issued at the airport at the time of check-in.
Korean Air Lounges may be unavailable at some airports. Other airlines' lounge facilities will be arranged for those airports.

Where do I pick up my hotel voucher at Incheon airport for the overnight stay?

Korean Air provides special promotional layover packages to accommodate layover passengers on certain designated routes, based on ticket conditions and travel dates. Once the accommodation is confirmed, the passengers are expected at either Arrival Information Desk or at Transit Counter upon arrival at Incheon airport for further assistance with the details of the hotel accommodation.