If you’re new to Pet Battles there is a lot you would need to do before getting to the Pandaren Spirit Tamer quest.
It’s a long chain of battles, but there are guides to help with pet suggestions and the routes to take.
You need to have made your way through all of the Tamers on all the previous continents you see.
Kalimdor for Horde, Eastern Kingdoms for Alliance, then Outland, Northrend, Cataclysm and then Pandaria up to Aki the Chosen.