Which counter should I go to get the free tickets after reaching Great Wall?

Fan, you should have a pamphlet together with your card. Didn't it say how to visit the wall? I am Chinese. I used annual cards to visit some attractions in Xian. There was no need to get tickets. They just swiped my card and let me in. When you arrive, you may find the staff there and ask how to use your annual card to visit the wall.