For tourism to China, you need to apply for a tourist visa in advance through CVASC in Brisbane. About the Terracotta warriors in Xian, you can visit Museum of Qin Terracotta Warriors and Horses https://www.travelchinaguide.com/attraction/shaanxi/xian/terra_cotta_army/ There are many links on that page that describe the history and procedure of making. And it is good if you will visit with a professional guide to the museum.