Buy bullet train ticket in Xian

Hi, I schedule to visit that city next Wednesday arriving there almost midnight. I saw from the above article that purchasing the bullet train ticket can be done from ticket outlets. Can I buy the ticket from Long Hai which it is opened 24 hours? I book for Xian Minxing Boutique Hotel which I think it is near Long Hai. If yes, do you know the exact location of Long Hai. Or I should buy the ticket at the railway station. Thanks