A month ago I flew into MAD T4 and simply could not find the arrival lounge

I tried to follow the signs but this brought me to the arrival hall landside and when I asked someone it was already to late (or too complicated) to go back in (where supposedly the lounge is). I'm flying there again next week and appreciate any hint, map etc. that shows exactly hot to get there. Every map or description I checked were quite ambiguous. Thanks.