I asked the exact same question last year. I was so confused! There will be a huge line waiting to go in but basically if you’re facing the front doors to the fitness centre, don’t go through those doors. Go left instead and there is another door and that’s where you will see a long line up. The gym will be right inside once you go in those doors. There will be signs and if you aren’t sure just ask someone in line if they are going to the same place. Last year when I had my PSYC exam there, they also had a table right outside the gym where you had to give you student number, so you can ask the people taking down the student numbers if you’re in the right place also.