In the Fengden Valley Club, there is an NPC of Shenlong Dealer near the warehouse. You can talk to him. There is a relatively large tournament plaque near this exchange merchant.

However, you can't change anything just by using the Xiaolong certificate. It takes 2000 fairy beans to change things, only lingshi. 2000 fairy beans need you to fight in the arena to get them. If you feel that your hand is disabled, try not to go.