She will confirm with instructions. Basically, it's the separate downstairs room at LSM (NOT the Harry Potter room), entrance outside in the back yard.
Walk through LSM (saying hi to Candy), exit the back door, turn right. 1st door.
or
Walk past LSM's front door, round the bend. Then, at the alley, turn left. First entrance in long pedestrian walkway* to back yard. Middle door (door to far left is toilet - don't get old).
or
Walk out of train station, left in front of the corner cafe, then right into the alley. Look for the walkway* near the far end.
*walkway is labeled alley on the photo just to confuse the semi-literate.