If you enter at the entrance at 31st and 8th you will just have to walk straight ahead and the lounge entry will be directly in front of you.
I believe there is a slight incline from the doors to the entrance of the lounge although it is very gradual.
I don't have a great photo, but this grab from Google shows the correct entrance at 31st and 8th that will be closest to the entrance of the lounge.