Travelling from Xiamen to Longyan

Hi, I need info on the following please:
1. How do I get from Xiamen International Airport to Xiamen railway station? Can provide detailed directions please?
2. Your listed 'Xiamen' station, does it refer to Xiamen North or Xiamen Gaoqi?
3. Do I simply book and pay for the tickets from your website? How many days in advance? What if I miss it due to immigration or flight delay? Can take the next available one if there's available seats? How to arrange for tickets to be delivered to airport for me?

My flight will land at Xiamen International Airport on 1st April 1pm.

Please advise, thank you.