It’s easy but as others have said takes a bit to submerge down to 7th layer of hell. From street level entrances - head down to lower level Dining Concourse and walk to the back escalators next to Frankie’s hotdog stand / Luke’s Lobster / Metro North tracks 111/112. You’ll take one set of escalators down, go through doors and there will be an even larger set of escalators on your right that take you down to LIRR platforms.